When both parties agree not to give gifts for an occasion, (usually Xmas) and then one of the parties gives one anyway (with or without warning/malice/regard)
I told my uncle Whatshisname to NOT give me a gift this year, but the fucker gift ambushed me. I chopped him in the neck, so we are even.
The act of fucking a girl doggie style while having a friend watch porn in a closet that you are facing. when your friend is ready to bust have him knock on the door. once you are also ready to go, pull out, spit on her back, and yell. Your friend will come out of the closet while the girl turns around and you nut in her face. when she turns away from you your friend will be right behind her and will ambush her with a nut shot.
when a man is having sex with a woman from behind and before he cums he pulls out his dick from her pussy and drops spit on her ass crack at the same time to make her think he is done then when she turns around to finish him off he blasts her in the face with his jizz
Being hit up for a charity donation at a store checkout register. Stores know that everyone in line behind you will think that you're a cheap assif you don't give. Ain't peer pressure great?