re: What's the absolute worst thing that can happen to you during sex?

My uncle, then a physician in the Navy, describes a night he had while on duty:

A Marine and his woman come in; he, with a bloody crotch, she with a battered and bruised face. My uncle is immediately thinking the worst and wanting to beat the Marine's arse for abusing his woman.

Until the story came out.

Ol' gal was going down on Jarhead Johnny. Ol' gal also happened to be an epileptic. During the fellatio performance, she suffered a seizure, and immediately bit down in to his dick. Jarhead Johnny furiously punches her face to a pulp because he is in agonizing dick pain.

She finally recovered and they went to the hospital. Still can't think of a shittier scenario.