We love really specific erotic scenarios that send guys over the edge, the more specific the better. For example:

Consider a pair of twins, separated at birth, who both go into porn as virgins and are filmed popping each other's cherries before discovering that they're long-lost brothers.

As Iain Davidson quips, "It's taken a while but incest porn has finally come into its own."

(Please feel free to share the specific erotic fantasy that gets you off.)