I have also had the engine loss thing where my opponent asks me if its gone and I said yes and he offered to leave me alone. I asked him to kill me because it was my own fault for pulling a stupid stall in a risky position!

I will generally allow an opponent to go if it is obvious he is attempting to retire (i.e. w/o eng.or wpns.) and the win is assured, unless it is Pokerguy (but that's kind of a personal debt sorta thing I'm trying to catch up on