If you have a mini-recorder I recommend you start carrying it around with you at all times and if you don’t have one, buy one as soon as possible for this gag. They are a great source of entertainment. Turn the recording device on whenever you are talking to people; eventually someone is bound to say something bad about someone else and then you have them caught. Pull out your recorder, stop it, rewind it a little, and then play the tape back for them to hear with a big smug smile that says, “you are in trouble now you stupid son of a bitch!” Their eyes will almost pop out of their head as they begin to realize what has just happened. They will say something like, “You aren’t going to play that for Laura are you?” You can either tell them they need to pay you $5 right on the spot or just walk away leaving them to wonder and worry what you are going to do with the audio clip.
I like to coax people into saying something bad about a mutual friend or coworker. “So tell me what you really think of Chuck, personally I think he can be very rude sometimes.” This gives your victim an opening to agree and comment. Where they usually wouldn’t have said anything, they now feel at liberty to go off on a tangent. I have found it very funny to pull the recorder out and watch their face as you hit the stop button and it makes that great “click” sound. Digital recorders today are very easy to conceal but I like the old fashion tape recorders because they make that loud “click” sound when you stop them. This way you get more of a response from your victim as you rewind the tape and they are given time to ponder over what they just said before you play the audio back to them.