Having the water in the toilet splash up and hit your ball sack and/or taint while taking a dump.
I ran in to the bathroom and dropped my pants just in time to unload a high pressure dump. If I didn't know better, I could have swore my dookie performed an epic cannonball from the high dive with the amount of Shitter Splatter I wiped off my sack.
Dude 1: "How hot is your new girlfriend Dawg?"
Dude 2: "Well, she did shitter to spitter with me last night."
Dude 1: "Fair play! What a fucking bad-ass ho!"