Answer: I've badly wanted to grab a "friend" by the hair and beat her face into the table over and over and over. And I once wanted to throw my roommate's guinea pig down the hall or step on it. I'd never ever act on either of those--for one thing, I'm not a violent person, I'm terrified of physically hurting someone. Probably because I'd get my ass handed to me afterward. Also, I love animals, and while it'd certainly be the most direct method to hurt her, it's not really fair to make the poor little guy suffer. Plus, she might come after my cat later...
I am, however, a very verbally abusive person. People confide in me and when they betray my trust, I'm able to restrain myself from ripping them to mental shreds with varying degrees of success.