The Stranger in The Killing Time" [http://www.imdb.com/title/tt0093347/].
The Orcs in the LOTR Trilogy. Or the Ring Wraiths. Or the Troll. Or Saruman... Well, pretty much anybody who'd kill those annoying hobbits, really.
Toad, while fighting Storm in the first X-Men movie.
First Boba Fett, and then The Empire in Return of the Jedi, ESPECIALLY against the ewoks!
Jango Fett (versus Mace Windu) in Star Wars: Attack of the Clones. If, while disrupting the execution on Geonosis by igniting his lightsaber, Mace Windu had shouted "Oh, I'm sorry, did I break your concentration?!", I'd have rooted for him instead, though.
General Grevious in Star Wars: Revenge of the Sith.
Tommy Lee Jones and Gary Busey in Under Siege.