1. Beholders - Big orbs of endless death. I love it!!
2. Evil Necromancers with a horde of undead minions that like to use minotaur skeletons to cut off a goodly sorcerer's head.
3. Lizardfolk - Reminds me of my first character...
4. Drow - What's not to like about evil, conniving elves?
5. Giants - They're just big. They wreak havoc among PCs.