The Krakatoa Eruption

Performed during intense doggy-style action, right as you're about to cum, you shove your thumb in your partner's asshole, yell "IT'S ABOUT TO BLOW!" like you're warning a Pacific island village, and immediately spray them with a sudden eruption of chocolate syrup (or any other sticky substance you've cleverly hidden nearby). Bonus points if you throw flour afterward to simulate volcanic ash.

"Bro, she dumped me after I pulled The Krakatoa Eruption, but it was worth it. Her cat is still licking up the chocolate."