When two guys are having sex at the top of a staircase. Right as the "giver" (aka man on top) is about to erupt, he pushes his partener (the "taker") down the stairs as hard as he can yelling "AVALANCHE!".
*note: if done on top of a sleeping bag, this move works like a gem.
Guy #1: "Dude, what happened to your nose?"
Guy #2: "I bumped it last night while gary was giving me the avalanche."