My favorite is when someone is snoring or tossing and turning at his seat and he wakes up 'cause everyone is staring or laughing, he gets all defensive and insists he was awake the whole time. Oh man I love that!
But what teachers should do about sleepers is a really good question. I figure if I let people get rest in my class then at least they'll be more alert in someone else's class. What is causing all this sleepiness, anyway? Too much homework? Too many activities? (Swimming excluded, of course.) Too many people up at night doing Facebook or (um) IM? If you want my opinions, ask me during the lock-in.