Lived for two years in Pinchot, one of the towers in East. The door jambs were pretty deep and we'd often stack an entire door jamb full of empty cans and tape one of the bottom ones to the door while they were sleeping. Next day when they open the door, they were jolted awake by the sound of cans clattering all over the tile floor.
Tape newspaper over the door jamb and leave a few inches open at the top. Fill the doorjamb up with popcorn, Styrofoam peanuts, crumbled paper etc.
My favorite was more of a scheme than a prank. Parents weekend, Sophomore year, a music major and I came up with a way to make some extra cash. We bought a bunch of sodas, cups, ice and penny candy. Rolled one of the pianos from the study lounges into an elevator and a cooler full of ice. He played the the piano while I poured drinks and handed out candy to every parent, grand parent sibling that got on our elevator for most of Saturday & Sunday. We cleared almost $500 in tips after paying for the soda, candy, cups & ice.