Well, my favorite Pokemon of all time is Empoleon, so I guess Empoleon!
Teh Flamin Chicken.
Treecko, Cyndaquil, Turtwig, and their evolutions.
Treecko, piplup and chimchar's evolution lines. Not really a fan of torchic, though.
empoleon is AMAZING
charizard and torterra
Charmander,Totodile and Treecko.
Bulbasaur, by far.
But all the Grass Starters and all the Water Startes (minus Mudkip) are high up there too. Also, Torchic.
In fact, the only one's I'm not extremely attatched to are the Fire ones, and even then, Cyndaquil's growing on me.