Beat

You may be looking for Beat from the Sonic and Mega Man Crossover event.

Beat is the main protagonist of Sega's Jet Set Radio series. He is a 17-year-old, laid back, and level headed "Rudie" that loves to skate and is okay with breaking the law. He is originally from the town of Fukuoka, and ran away from home like many other Japanese Rudies. Beat spends his time skating around fighting for turf with the rival gangs of Tokyo-to, marking his territory with graffiti and annihilating others' tags. As graffiti is an act of vandalism and is punishable by law, this attracts the attention of Police Captain Onishima (and Hayashi in Jet Set Radio Future) and his S.W.A.T. team, who relentlessly pursue Beat and his friends.

Jet Set Radio
The original Jet Set Radio, released in 2000 for the Sega Dreamcast (renamed Jet Grind Radio in North America), is introduced by Professor K, the dread-locked and street smart DJ of a pirate radio station called "Jet Set Radio." Professor K explains the events that go on in Tokyo-to and guides the player throughout the series. The game begins with Beat starting his own gang known as the GGs and looking for recruits, after he was rejected time and time again by the gangs of Tokyo-to. With his skating and graffiti skills, he impressed fellow Rudies Gum and Tab in the Shibuya-cho district, who decided to join him, forming the GGs first three members. From then on, several other Rudies joined their gang after seeing their success in the city. Sonic and friends also make cameos in the game, in which the player could download images of the character artwork from Sonic Adventure to use as graffiti for tagging. This was done by connecting to the Internet through Sega's former online service, SegaNet. Sonic even appears on a billboard in the game's ending cutscene.

Jet Set Radio Future
The game's sequel, Jet Set Radio Future, was released in 2002 for the Xbox. In the game, Beat is replaced by Tab (now called "Corn") as the leader of the GGs. The GGs struggle for control in Tokyo-to, which is being oppressed by the mega corporation Rokkaku Group. The Rokkaku's leader, Rokkaku Gouji, the main antagonist of the series, is now mayor of Tokyo-to, robbing the citizens of freedom of speech and expression. And so Beat and the GGs continue in their mission to "bury Tokyo in graffiti," fighting the corrupt Captain Hayashi and the Rokkaku Police.

Sega Superstars Tennis
In Sega Superstars Tennis, Beat and one of his close friends from the GGs, Gum, appear as playable characters. Their designs are taken from the original Jet Set Radio. Beat's Superstar move has Combo, a member of the GG's who's always carrying around a boom box, grind on the net of the tennis court while spray painting on the opponent's side. The paint trips up Beat's opponent, and distracts them from the game. Gum's Superstar move has Tokyo-to's police force storm in on the tennis court, running over her opponent.

Sonic & Sega All-Stars Racing and Sonic & All-Stars Racing Transformed
Beat also appears as a playable character in Sonic & Sega All-Stars Racing, where he drives an orange and red customized street racer called "De la Custom GGs," named after his gang. It has an extra stereo system and neon underlights. In this game, his design is taken from Jet Set Radio Future.

In Sonic & All-Stars Racing Transformed, His Tuner gets replaced by a quad bike presumably made for the streets, with styling after himself, his gang, the GGs and his game's titular radio station, Jet Set Radio. Being that the main focus in this game, aside from racing is transformations, his bike does transform. As a boat it looks strange, with the wheels being replaced by skis, like a snowmobile, but instead of treads that complete this 'snowmobile', there are a set of propellers at the back, thus making it a jet ski, or a Seadoo. Its jet mode is a hover bike, with flipped up wheels and two small propturbo engines, reminiscent of Back To the Future Part II. In this game, his design is taken from Jet Set Radio.

Trivia

 * Beat is one of five human non-Sonic characters that appeared in at least one Sega Superstars game, the others are Billy Hatcher, B.D. Joe, Akira and Ulala.
 * In Sonic & All-Stars Racing Transformed, Beat is one of only five characters to drive a ATV, the others are Knuckles, Metal Sonic,Joe Musashi and Gum.
 * Beat is the only non-Sonic character to have a completely different design between games in the All-Stars Racing sub-series, having his Jet Set Radio Future design in the first game, racing a street racer themed after his Jet Set Radio appearance while in All-Stars Racing Transformed, he has his Jet Set Radio design while racing a quad bike themed after his JSRF design.
 * Beat is the only character (as well as Joe Musashi) in Sonic & All-Stars Racing Transformed to come from a real world location.