I actually have three faves lol.

Archeops because I loved dinosaurs at a young age (and still do). Plus, those colours are bomb, especially the shiny one.

Hydreigon because (1) colours are bomb, shiny's are alright. (2) Huge dragon lover. and (3) is a total beast competitively.

And Druddigon because, again, colours are bomb, dragons are [ok hand emoji], and defense Drudd w/ Rough Skin is OP.

and basically every other gen 5 pkmn because i have lots of nostalgia for it.