a magic trick of sorts, when you are banging a chick from behind you fake an orgasm, pull out, and spit on her back jerking off all the while, you must time it right so when she turns around thinking the love making is over, you cum right in her face!
Your murderers might come to you with a smile, but most of the time they are not still wearing one at the time they kill you. A smiling gunman is rare.