One of my co-workers is excellent to play little office pranks on. Past pranks include tampering with her phone so that she hears the person talking but they can't hear her. Another time, a co-worker somehow got to her lunch and took a bite out of her apple and just left it there, bite and all.
I've decided that I want to start keeping some candy at my desk for a little snack for my comrades. However, candy is expensive so I'm just going to take the candy out of her dish and put it in mine.
This is very amusing to me. I know she'll flip and I can't wait.