Well...
Last year, Eliot Sihn's hand suddenly became sentient, and able to detach itself from him on its own volition. This sort of goes back to his origin - he was born without a left hand, but he managed to "grow" one due to his regeneration. He also had powers that allowed him to detach body parts, but the other parts didn't need to be cajoled into re-attaching.
I don't think this is the kind of thing a GM would typically do to a player, but I, and the rest of the group, loved it, and Zornwil is not a typical GM. It became a vehicle for personal growth for the often overly-ruthless Sihn, as he couldn't quite bring himself to snuff it out. "Lefty" developed into a key DNPC, figuring into several plots. He started off quite innocent and childlike, but he's started to mature a bit over the last sessions, and, sniff, Sihn has decided that it is time that Lefty moves on - he's been accepted to Prof. Xavier's School for the Gifted. We'll miss him, especially since he's become the best friend of one of the other PC's. It was always interesting making sure Lefty was rounded up in time for a super battle - when you carry an OAF, you need your off-hand to hang on to it. I'm sure Lefty will still show up in a lot of up-coming sessions. Sihn will finally replace his hand - a trivial operation for him.
Other characters would deal with it fine - I have a tendency to play swashbucklers, and replacing a hand with a hook, or some sort of swiss-army-knife gadget would just give them more roguish charm - several of them had hook-hands during initial design, it just has never made it into any final designs. My super-brick, "Crete! The Man of Living Concrete!", would be pretty much immune to such an injury, but he has enough normal difficulties in his every-daylife that replacing one hand with a stub would hardly be noticed.
Lamrok