ok, here's a personal one. In high school, my friends and I used to troll the local grocery stores. San Antonio has tons of live oak trees, and one year there were a ton of acorns on the ground, so we stuffed our pockets, and then reverse-shop-lifted them by putting them in a produce bag and trying to buy them from the store. At the first place we did this, they ran all over trying to find the price of acorns before a manager finally charged us $.50/lb
We spent about $1 on our own acorns.
The next place wanted to charge us $4.99/lb at the "mixed nuts" price. We left without them and told them they could just put them back
The best part was always the other shoppers in line... because we always chose the longest line we could find when doing dumb stuff like this just to get a rise out of other shoppers. One customer looked at my bag of acorns on the counter and said, "Can you cook with acorns?!"
I just looked at her. Really I was trying to come up with an answer without cracking a smile, but before I could say anything, she shrugged and said,"Yeah, I guess you can". I almost lost it, but somehow managed to deadpan my way up to the cashier.