As discussed in "The 40 Year-Old Virgin," a win-win is the act of popping any kind of drowsiness inducing drug (Nyquill for example) and proceeding to jerk off. Whether or not one finishes before falling asleep is besides the point because "either way you win..."
Rob: "You going out tonight man?"
Gene: "Nah I'm staying in tonight. I'm pretty tired."
Rob: "You going for a win-win?"
Gene: "Great idea!"
A win-win situation is where all outcomes are desirable.
If you kill him, you'll get respect and the cops won't touch you.
If you don't kill him, someone else will whack that asshole..