There's a few awesome concepts I've created for various LARPs and tabletops and fanfiction, including:
1. The celibate, constantly disgruntled monk who was essentially like a shirtless, bald Jet Li. He would basically walk up to things and punch them in the face. Literally. It didn't matter what it was. Knight who's trying to take his party captive? Punch in the face. Bear? Punch in the face. Troll? Punch in the face. Hellhound? Punch in the face. One of his team members trying to steal from the dead? Punch in the face.
Much fun was had by all after that. Especially because the GM also kept trying to get his pants off.
2. A squid girl. Enough said.
3. The Trio, a band of assassins just short of sane. Two of them are brother and sister who are a little too close to one another, if you catch my drift. The sister speaks in rhyme and has a thing for things that explode. The brother's just a dirty jerk who contemplates branching out into questionable business on a frequent basis, if you know what I mean. The third member, meanwhile, is an actor who likes to torment his victims with mind games.
4. A mime (technically, a giant, living ceramic puppet -- as in, complete with strings with which people could control her) who liked to freak people out in order to feed off their fear. She could also walk into people's nightmares, and some of the things she created may or may not be able to come to life. (For example, there may or may not be an invisible box of equally invisible grizzly bears in her city.) And, oh yeah, this was in a LARP.
There's a few others, but I think the above are some of my best.