I had two the other week for professional club girls u17's teams.
First one was in the (completely useless) assistants area, stared at him, he started to wave the flag as if for a pen, so I blow the whistle and point to the spot by as I do, the assistant points to the corner flag, I'm thinking WTF, players saying its a corner, I go over to have a word (walking backwards of course) ask him, what on earth the signal was meant to mean, he replies with a grunt and I managed to hear in the muffles that he forgot the new signal and it's a penalty.
Second one, red is sprinting about to go 1v1 with the goalkeeper, yellow defender catches up and somehow collides with her own goalkeeper, there is a bit of a tangle then the goalkeeper dives at the feet of the red striker, who only takes the striker down, but doesn't get the ball, I point to the spot, next thing you know all three players are on the floor, twelve minutes later we restart with the penalty, the goalkeeper having to go off as she cant remember the incident, defender having to go off due to a bad leg injury, but the striker fine, ironically the striker was the penalty taker but she couldn't take it as she had to go off because a physio came on to check her over!