One time I was DM-ing for a group of friends, it was late and we were drunk. One of my friends had left a glass behind my dm screen were I couldn't see it (but I knew it was there). I don't remember exactly how, but he bumped the screen and the cup fell from the table
Somehow my hand jumped in an arc going over the screen and under the table to be exactly were the glass was on its way to the floor and I catch it