Quoted By:
Deoxys.
Would try to be as bro as possible... but it wouldn't be friendly as such, due to the fact the pokémon has a (literally) alien personality I would think.
Still, going around fucking people up with my mutated virus would be pretty baller.
If not deoxys I'd probably pick Regigas and ride around on his shoulder as we quest to find the rest of the regi trio / his underlings.