I adore writing as villians. At the moment, I'm writing my first Pokemon fanfic, and the villian I had to start off with was a Crawdaunt. He is now dead, and the Pokemon to take over his position is yet to be announced to the fic readers, so I won't spoil it. :3
But the other 'evil' characters I have in the fic are an Ambipom, Donphan, Skarmory and Noctowl. o.o
So, I don't really use obvious choices.