This is a good prank for that evil ******* (EB) in your dorm nobody likes:
Most dorm rooms have doors that open inwards (into the room instead of into the hall). The day before the EB has a morning final exam, buy (or otherwise acquire) approximately 500 disposable cups. That night (and by night, I mean 3am) organize with your friends to meet in the closest washroom to the EBs dorm room. Fill the cups with water or... use your imagination. For this next part, being absolutely quiet and quick is the key. Stack the filled cups against the EB's door - stack 'em high to at least the door handle, and stack them sloping out from the door, like the classic display of cans in a grocer's. The next morning, the EB opens the door and... well, just make sure you have your camera ready.
That's all well and corny, but here's another one if you really want to establish a legacy on campus, but it's subtle. I can only claim credit to bearing witness to the perpetrator for this one:
At York University (Toronto) campus in the mid-90s, there were conveniently placed sign posts all over the place with useful directions telling students and faculty and visitors where everything was. You know: name of building, and an arrow pointing the direction. The reason this prank worked so well is that the lettering on the posts was quite small, as it was intended to be read by pedestrians who already happened to be walking along the path near the posts. The prankster studied the font and manufactured a match. For over a decade, in addition to the legitimate directions on the posts, students were being directed to exotic locations like Vagina Hall.