5. Spike
Spike became nothing short of iconic in his time on Buffy the Vampire Slayer and Angel. Played by the brilliant James Marsters, his strange mix of charm and brutality made him a complicated and unpredictable character who, despite his introduction as a slayer-killing evil-doer, became widely loved all over the world. He was one of several big bads in season two of Buffy - along with Angelus, Drusilla and the Anointed One - but his story was a simple one (he arrived in town to kill a slayer for the third time, essentially) and it could quite easily be condensed in to a movie. Replacing Marsters would be a near impossible task for any actor, but if someone can even come close to replicating the character's charisma he would be a sure fire hit with movie audiences. With Drusilla on his arm and a gang of flunkies backing him up, his quest to make it a hat-trick of slayer kills would make for a really cool movie plot.