Usopp is a tanned, skinny teenager with black curly hair and a long nose, which is apparently an allusion to Pinocchio, a wooden boy from a story of the same name who possessed a nose that would stretch after he lied. He usually wears a dark yellow plaid bandanna, special sniper goggles, brown overalls with a white sash and no shirt underneath (although he wore a green striped shirt during the Skypeia Arc). Usopp inherited his famous nose from his mother, while the rest of his face closely resembles his father's.Oda claims that Usopp is most represented by the armadillo.Oda has also said that he uses the color yellow to represent Usopp, and he smells of gunpowder.
PersonalityUsopp is one of the more sentimental Straw Hat Pirates, and cries or loses his temper in moments of emotional stress. At the start of the series, Usopp was an easily frightened, anxious, insecure, compulsive liar. Unlike Nami (whose cowardice is linked to just wanting to stay alive), Usopp's cowardice is the result of his fear and insecurity, especially when faced with uncertainity. Though Usopp is a coward by nature, he is able to put aside his fear during more deseperate times: despite being afraid, he faces those fears for the sake of his friends and sometimes people he barely knows. Most of his lying was intended to make him feel better as Usopp is easily overwhelmed by his opponents, such as Aokiji, and usually ran from them. He is the first to come up with an excuse not to do something to avoid putting himself in danger. One of the most frequently used excuses is that he gets a disease named for example "Can't-get-on-this-island disease".
It is this which leads to his feud with Luffy - specifically his refusal to part with the ship he had come to love. This was the result of all his insecurities about his usefulness as a member of the crew culminating within him finally exploding under the stress of having just been beaten near to death by the Franky Family and then losing his ship. Especially when compared to Luffy, Sanji, and Zoro, Usopp is not very strong in the physical sense. Though he is very intelligent and a talented sniper, he had trouble seeing his better qualities and his strengths, until the fight at Enies Lobby opened his eyes.
After meeting the giants Dorry and Broggy in the Little Garden arc, Usopp wants to travel to Elbaf one day and meet the proud warriors there. Usopp gave his first glimpse of understanding the ways of the warrior and the pride of a duel during the giants' battle. As a result Usopp often sees the Elbaf warriors he has met in his travels as sources of inspiration in his journey to become "a brave warrior of the sea".
Throughout Thriller Bark, many members of the crew fell victim to the effects of Perona's negative powers, causing them to become incredibly depressed to the point where they can't move. However Usopp, though slightly effected by the power, got to his feet claiming he could not become negative, because he already is negative/depressed, even saying it in a brag-like way. Perona claimed he was the only person who was ever immune to her powers, so she fled from him in fear.
He also has a dislike for mushrooms, due to eating a poisonous one when he was younger.
Alter-EgoSogeking is Usopp's alter-ego developed during the Water 7 and Enies Lobby arc. When he left the crew, later seeing the others trying to save Robin made him feel guilty for leaving. He stated to Sanji and Franky that he cannot help them fight for this reason. He hastily 'disguised' himself in a mask and cape and began calling himself "Sogeking, the King of the Snipers". During this facade he sometimes dons a deeper voice which can be seen as the "true" Sogeking. Sogeking also refers to nearly everyone with a "kun" suffix (Luffy-kun, Zoro-kun, Chopper-kun etc.) and when asked of the whereabout of the 'Island of Snipers' he supposedly comes from, maintains that it exists "in your heart". Everyone except for Luffy and Chopper already knew that Sogeking was Usopp at the sight of Usopp's significantly long nose. Onion, Carrot, Pepper and Kaya were able to recognize him, though they claimed no one else in Syrup Village did.
As his alter-ego Sogeking, Usopp was able to fight alongside the others without having to deal with his departure. During his time spent acting as Sogeking, Usopp began to realize that while he was one of the weaker crew members, his role as the crew's sniper and a supporting crew member make him more valuable than he thought. Ultimately, he has been recorded as Sogeking on his bounty. The fact that Usopp himself is not technically wanted allows him to slip through enemy lines seemingly undetected. Oars originally let Usopp go because (being Luffy's shadow) Oars did not think Usopp was a target.
During his fight with Perona, Usopp showed signs of a split personality and even went so far as to argue inside his head with his alter ego over their situation.  Although they are technically the same person, Sogeking in comparison to Usopp is much more confident and took over once Usopp adorned the mask again, only slipping back into Usopp once the mask came off.  Whether or not Usopp is developing a multiple personality disorder is debatable and has yet to be confirmed by the author or within the story.
CrewHe will often goof off with Luffy and Chopper and shares a strong, brotherly relationship with them. He and Luffy share a common path towards an eventual meeting with the Red Haired Pirate Crew: Luffy to reunite with Shanks and Usopp with his father. Through this small connection and the fact that they are the same age and thus, at the same level of maturity (in their own special ways), Luffy and Usopp had a very special bond from the moment they met. Chopper loves Usopp's stories and often falls for his tall tales, and Usopp in turn loves Chopper's hero worship of him and makes a point to act cool in front of his "younger brother." Both Luffy and Chopper were very upset when Usopp left the crew.
He likes Nami as a sister, but (like Chopper) is often intimidated by her more ruthless behavior. Usopp and Nami have a special bond as the only "normal" crew members. At some point during the Arabasta arc, Nami approached Usopp and asked him to make a weapon for her, convincing him to do so by confessing her feelings of inadequacy when compared to the awesome strength of Luffy, Zoro, Sanji and even young Chopper. She said that Usopp was the only one who could understand these feelings, and thus was the only one who could help her. Zoro and Sanji get on well with him, but often admonish him for his cowardice and sentimentality. During the Enies Lobby Arc Sanji sowed a special bond with Usopp as he helped him realize that he wasn't useless to the crew like he previously thought. Usopp was scared of Robin, as well as Brook when they appeared with the Straw Hats, however, he changed his views over time and see them as good friends. As for Franky, while he did beat up Usopp during the Water 7 arc, they began to understand each other once they talked about the Going Merry. Usopp is usually the one who tests Franky's cannon-type inventions. A running gag involving Usopp and the crew is whenever a topic of one of his personal traits (such as his lying habits or his nose) comes up, the crew always refers to him (like in Jaya with the tale of the King of Liars Norland, or when they first meet Kaku).
FriendsHe shared a deep fondness for Kaya back in his village due to her losing her parents and often tried to keep her happy. Unfortunately, his lies backfired when he tried to protect her when Kuro put his 3 year plan into action and Kaya lost all respect for him. After Kuro's plan is stopped, she decided to try to remain happy for him while he was gone and Usopp is left happy that she is safe.
Back at the village also, his old pirate trio also await his return. When they last met they parted ways with him to led off on their own dreams. They have been following the reports of him ever since via the newspapers and are proud to have called him captain, even if the other villagers don't know what has become of him. Kaya also states how proud she is, and that she eagerly awaits his return to her and the village.
"Sogeking" also made friends with Oimo and Kaashii after he revealed the truth to them concerning the World Governments lie about having their leaders.
EnemiesHe has a deep anger at Kuro, whom he defeated to protect Kaya. While he himself is at ease with the Marines, his alter-ego carries a bounty. He also made an enemy of Perona during the Thriller Bark arc for being the first person to defeat her.
Yasopp is Usopp's father. While Usopp has yet to be shown interacting with his father, Usopp has remained proud of him even though he took the path of a pirate. It is also unclear as to how well he knows his father, as it was never said when exactly Yasopp left ( except for the flashback during the fight between Usopp and Daddy with Yasopp saying " I left when he was just a baby.") to sail with Shanks' crew. Usopp either knows about his father from stories told by his mother or from actual memories, which one it is remains a mystery. Yasopp also seems to care deeply about his son despite being absent for the majority of his life.
BanchinaBanchina was Usopp's mother. He deeply cared about her well being, to the point of creating his original set of lies about his father returning in order to keep her alive. When she died, he suffered a deep loneliness that led him to keep on lying even though he no longer had a reason to do so.
Abilities and PowersUsopp's role in the crew is Gunner and marksman/sniper, just like his father, Yasopp. For a long while, Usopp's sharpshooting skills were downplayed and somewhat overlooked. This is due to the fact that he is so high-strung and jumpy, that he often gives into his baser instincts of survival: fight or flight (usually choosing flight). However, with the birth of Sogeking and during the battle at Enies Lobby he displayed just how skilled he is at sniping when he saved Robin from an incredible distance, shooting down the marines and Spandam. One marine was so shocked that a sniper was taking them down so accurately from such a great distance and with the wind blowing against Usopp's favor, that he asked, "What the hell IS he?!" Proving that Usopp certainly isn't just your average guy. He also may have unusually sharp eyes not only in sniping but in observation. When Moria appeared in Oars' stomach, Usopp immediately noticed while the others had no idea where he was.
Prior to the introduction of Franky (as well as the creation of the Clima-Tact), Usopp served as the Straw Hat's sole unofficial gadgets specialist. His creative engineering has resulted in both the Clima-tact and Kabuto. Though he is creative, his engineering skills are limited beyond this level of inventiveness. For other more complex activities, such as acting as the shipwright for the Going Merry, he is largely inexperienced, as he was barely able to keep the Going Merry going using patchwork repairs. As Franky pointed out, his skills are amateur and he barely knows how to use a hammer correctly for such jobs.
One of Usopp's useful attributes is that he is an extremely fast runner, even faster than Luffy and Sanji. Though it is shown that his stamina when it comes to running is practically limitless (after running for miles he isn't exhausted in the least while Chew, a Fishman, is tired). In the Little Garden Arc, Usopp was seen running from one side of the prehistoric island and reaching the other side in a matter of seconds. His lightning speed was enough to even surprise Admiral Aokiji, when Usopp saved Robin from being crushed. He uses hit and run tactics, and works best as part of a team where there are more physical fighters to watch his back and vice-versa. Although, like Chopper, he sometimes has trouble thinking on his feet, his tactical skills have proved instrumental in more than one battle. Usopp, like Nami, has been able to use his intelligence and inventive tactics to defeat enemies far stronger than himself. However, though he has survived every fight so far this way, his fight against Luffy only served to prove what separated him from other crew members in terms of overall combat strength.
He also seems to be naturally adept at absorbing massive punishment, as he often comes from which either brutally injured, or left at a near-death state (or close to passing out), but can be seen shrugging it all off like they never even happen in the next scene. This was particularly evident when he fought Perona, where after using an Impact Dial on one of her zombies (which likely dislocated or broke his arm) he immediately used that same arm to aim another of his pellets at Perona. He also managed to use an impact dial in the middle of his fight with Luffy without seeming that affected by it, and he was already gravely injured from being beaten up by the Franky Family. Another example is that Usopp survived being hit in the face by Mr.4's 4 ton bat (Ms. Merry Christmas said that most people should be instantly dead when hit by that attack). Not only did he survive, but he was still able to fight. He also stated, just like Luffy and Sanji that he has never been ill during his life (which impressed Vivi). 
Usopp is also a great artist, he proved that in the beginning of the series when he made "his" and the straw hat Jolly Roger. (Seeing that Luffy's art lacks talent.) Also when Luffy and chopper make snowmen or sand castles it usually shows Usopp after wards with a snow statue or a more detailed castle.
Usopp has outstanding marksmanship abilities with a slingshot, and is probably on his way of becoming one of the best marksmen in the One Piece world, which is the primary reason why he serves as the Straw Hat's Sniper; and often tasked with the managing of artillery weapons like cannons of their vessels, most notably the Thousand Sunny's Gaon Cannon, which is dangerous on its own, but with Usopp's long-range skills, it is deadly. His slingshot is his primary form of combat, and he has many different types of ammunition which he carries in a large purse-like shoulder bag. He uses eggs to blind opponents and rocks in the slingshot when out of ammunition. He is also extremely durable, able to absorb unbearable amounts of damage (he once got struck by a four ton, metal baseball bat to the head only to continue fighting minutes later) and sometimes uses his hammer for close combat in an unskilled, frenzied but effective attack.
His ammunition, called "stars", has great range, from rotten eggs and hot sauce to shuriken and powerful explosives. Usopp has other attacks unrelated to projectiles, though they are mainly jokes. These include the 5 Ton Hammer (which is actually only about 5 kilograms) and Usopp Noise, where he plugs his ears and scratches a chalkboard. Also, recently his "5 ton hammer" has become a "10 Ton hammer," possibly to symbolize a certain increase in strength as time goes on, though he's still considered physically weak when compared to the rest of the crew, except for Nami. He has also recently started using Skypiean dials for attacks (and had steadily shown growing aptitude with each battle in which he utilized them), such as using the Breath Dial to house explosive gas, using the Flash Dial to blind his foes, and using the Impact Dial to absorb and reflect blows.
Usopp improves his sight with special goggles. He purchased an upgraded pair in Loguetown, but the actual scene of him purchasing them was cut out in the 4Kids Entertainment dub. The scene was also absent in the original manga due to lack of room