phond dipping

Leave easily mistaken receptacles around for people to accidentally deposit specific items in for you, or others, to collect later.

(I might have done this by accident today: I picked up my coat from the work hatstand, to later find a pound coin in there which I don't think belonged to me. If it wasn't mine, someone must've put it in there assuming they'd got their pocket, when in fact they got mine.)

Obviously you could use this technique to be mean, or you could use it to exact some sort of vigilante justice on very specific target audiences, or just to generally snicker about being subversive.

You could also imagine a social game version of it, whereby people notice said masquerade receptacles around the place and deliberately fulfil them, as a sort of push-pull version of the traditionally push-only generosity game.

Perhaps I prefer that variety: a sort of hidden cache game whereby people who know the game and the specific signals can pick up free bonuses, and give them out :)