A game somewhat popular in Southern California (specifically the 760/909 area codes)
The objective of the game is to say the words "Slider Justice" whenever your friends are zoned out or not paying attention. If they don't realize you've said slider justice, then you slap them in the face.
If used responsibly, it can be quite hilarious. But if abused, it can really be annoying.
You: *whispering* Slider Justice.
Friend 2: Huh?
Friend 2: God damn high kill