Christopher - Unmake Plastic
(As an aside, I once gifted a fist-sized D20 to a player who rolled, veiled behind hand, an inordinate number of critical hits. They never used it.)
I had a player who brought the most infinitesimally small dice imaginable, clear with unpainted numbers. He would make his roll, immediately scoop the dice up, peer at it, and throw them down in disgust while announcing "I missed" or "I failed". Many times I'd pry the roll result out from him and discover that the result was actually a success. The platonic opposite of a dice cheater.