While receiving head (preferably with your partner on all fours, not on knees), ball your hand into a tight fist and hit your them as hard as you can in the rectum, directly before ejaculating. Not only is this hilarious, it also feels great.
John: "How was last night with Tom?"
Kate: "It was great until Tom hit me with the Armenian Sledgehammer."
John: "Ooh... that sucks."
Kate: "I won't be able to sit right for a week."