Kalen. Don't think she posts here too much these days, but they don't come any tougher. It's a known fact that if every one of us were to fight Kalen, she would still win. In fact, if 5,000 Leeza's were to take her on, Kalen would still come out victorious. She's quite immense. She also has a massive galaxy tattoo sitting on top of her cleavage, and something tells me she went through a whirlpool of pain to get that done. I think she's also a black belt, although I'm not 100% sure.

Otherwise, well, Knox is in the US army and has been for some time. I imagine he's pretty tough. Same with theundeadhero.

Other notable mentions: CloudSquallandZidane appears to be buff, Dan (DK) could likely do some damage and fireman Spaceman Spiff probably has a bit of muscle on him.