Crossbones from Captain America
Venom from Spider-Man
Mark Hamill as the Joker, Hobgoblin and the Trickster
Alex Krycek and Eugene Tooms from the X-Files
Ricky from Better Off Dead
Biff from Back To The Future
Rowdy Roddy Piper
How could I have forgotten Biff? Seriously I can't believe I forgot him with how many times I've seen the Back to the Future movies. Oh and Kryceck and the Smoking Man without a doubt are two more I forgot.
I liked the Cigarette Smoking Man, but the more they fleshed him out, the less intriguing he was. Krychek was always cool, though.