I had an NPC in Dark Sun who was a vegetarian. Of course, everyone assumed that meant that he was somehow less violent and murder-happy than the run of the mill cannibal halflings.
Wrong!
Eventually, he would attack and say something like "I'm not going to eat you--just kill you!" (and get a surprise round attack).
I used him in several games. The players always relaxed when they found out he was a vegetarian. Ah, good times.
Then you might dig this! Clutch, "When Vegans Attack":
[ame=http://www.youtube.com/watch?v=fZRwyTClxd4&feature=youtube_gdata_player]Clutch - When Vegans Attack - YouTube[/ame]