I had a guy hand me a $20 for grabbing his gate check bag while doing the post flight. He had a tight connection and I'll do this from time to time if the pax asks nicely or if the rampers are being insanely slow. He slipped it into my pocket and took off up the jetway. I usually wouldn't accept it but he must have been in a hurry because it was a full sprint. I was expecting to see a dollar or two.

I used it to buy starbucks for the crew.