Lickitung!
OOOOooooOOOOoooohhhh, yeah baby, do yo' thang!
Okay, so awkward/funny/perverted/stupid comments aside...
I've only played Pokémon Blue, so I only know, 150 (151?) pokémon.
Truth is, I found it a decent RPG, but not as brilliant as everyone claims, i.e. overhyped.
And as a gamer who's been around, I must say, it is kind of a Megami Tensei rip-off... For children.
Now, to get back on topic before I'm flamed to death:
I'd go for Cubone, later to turn into Marowak (been I long time, but I believe that's how it is spelled).
Because wearing your own mother's skull as a helmet is pretty cool.
EDIT: Ninja'd by SamiePC.