Bothering Snape
Take him to meet Grawp, saying you'd found a dead acromantula in the Forest
(No, Sir, I don't know how I got there, I was napping and woke up...)
Introduce him to E Bay via 'What I bought on E Bay song'
Sing High School Never Ends whenever he's nearby
Enchant his cauldron to play The Emo Song whenever he uses it
Use medieval technically allowed swear words when addressing him
Play Barbie Song when he walks into the classroom
Use a color changing Charm to make his hair beach blonde
Leave him a fake note from Draco saying that Draco was going to live in the Muggle World
Cast an illusion making it look he's surrounded by snogging students
Put him in a pokeball
Imperio him to wash his hair
Curse him to stand up in the great hall and sing the Barney Song
Make snide remarks about traitors
Curse him with a 24 hour notice me charm
Run away screaming 'it's Frankenstein!' when you see him
Follow him for a day playing mini snape and smile angelically if he turns around, pretending to be busy
Curse him into professing his love to Pomfrey at dinner
Make him think he's gone mad and is surrounded by fluffy pink bunnies
