A disgusting druid of the god of pestilence and decay, who uses poisons and biologically engineered diseases to wipe out all those who are not racially pure.
[ My players hated this guy with a passion. ]
A tall, sunburnt, raspy-voiced ranger/assassin kitted out with numerous defensive and movement-based magics that allow him to cheat death time and again.
[ This guy survived a half-dozen encounters with the PCs before they finally slew him. ]
A ruthless, amoral dragon-hunter who manipulates the PCs into helping her locate the lair of a good-aligned dragon.
[ OK, I ripped that one off from Dungeon magazine, but it's still sweet. ]