Dib from Invader Zim, because I play Dipper Pines. It'd probably start off as a friendship rooted in being mutually socially awkward and them both having a love of investigating the paranormal...and then end in a bitter, bitter rivalry as Dipper's naturalist/conservationist attitudes towards most of the paranormal that isn't Bill and his henchmaniacs, and sympathy for creatures like Multi-bear, clashes with Dib's desire to violently dissect the paranormal and pull it apart to see how it ticks.