Raw Eggs
Place raw eggs under the person's pillow or comforter or somewhere else that is bulky enough that the eggs won't be noticed until after they have been crushed. This is lots of fun to clean up after...

Crumpled Up Newspaper Filled Room
Fill a person's room while they are out with massive quantities of crumpled up newspaper. This takes a fair bit of planning, a lot of paper and a small room but can have good results.

Door Swap Prank
Remove doors on your hall and swap them with other doors from around the hall.

Dorm Room Door Prank
Cover a person's door with butcher paper and fill the space between the door and the wall with confetti, peanuts, etc.

Nasty Messages
Write all sorts of nasty messages in permenant marker on a persons body while they are asleep or passed out drunk. Put them in hard to cover up places.

Appliance Timer Prank
Use appliance timers to detonate stereo equipment at high volume.

Dump On A Plate
Take a dump on a plate and stick it in the microwave. The area will smell for weeks.

Staples
Staple the cuffs of your dorm room buddy's pants together.

Red Hot Blister
While your roommate is sleeping, place a couple of Red Hot hard candies between their teeth and lips. They will wake up with a very bad blister.

Clear Tape On Eyes
Apply some clear tape to your roomie's eyes when he is sleeping, wake him up, and and ask if he feels all right.