Impmon

A tricky Digimon who lives in the human world and seems to have it in for the Tamers. Once belonging to two young kids, he left them to live on his own and gain power.

Despite his small size, he is fairly powerful (though he runs more than he fights) and can blast enemies with fire-based attacks. Not truly evil, yet not quite a hero either.

[Spoiler] He manages to evolve into Beelzebumon (with motorcycle and dual guns) in the Digital World, but still loses to the Tamers. Once he reunites with his owners in the human world, he transforms into a more powerful version of Beelzebumon, armed with a hand-cannon and wings. [/Spoiler]