useful auxiliar tip: the 15-minute back pocket exercise

Keep a back-pocket full of 15-minute activities, exercises or simple games that you can whip out at a moment’s notice. It should be something that is suitable or easily adaptable for all levels, and doesn’t need any special materials or equipment. Invariably, you will find yourself in a situation where the teacher has deserted you or you have extra time on your hands at the end of a previous activity. I call them 'gaping hole' moments. You don’t want gaping hole moments. A few of my favorite 15-minute activities: Celebrity, Jeopardy!, conversation cards, and a little game I like to call 'Say It, Spell It, Count It'. With this game, I write different words, numbers, or simple math problems on slips of paper. Each student takes turn pulling a slip of paper from the bag. They have to either say the word in English (it's written in Spanish on the paper), Spell the word in English (also written in Spanish on the paper), or count something (i.e., say a number or give the answer to a simple problem).
What sort of 'gaping hole' activities do you use with your classes and private lessons?