The lean, mean, slashy Pokemon tend to be my favourites. So that's:
Sandslash (Sandslaaaaaaaaaaaaaaaaaaaash!)
Scyther
Weavile
Kabutops
Shiny Charizard
And then the not-so slashy:
Pikachu (Yeah, I know he's the obvious choice, but the first game I EVER owned was Pokemon Yellow, so he has to be one of my favourites. I have no choice.)