I've moved past the small little gags like the toilet seat and fake poop, but they are fun if used correctly. Here's my list as of today, but I doubt it will remain unchanged...
1. Paper cup pyramids infront of bedroom doors. Luckily, their doors all open into their bedrooms. I plan on using about 200 cups per door (3 doors) and filling random cups with water, so they can't just bulldoze through it. I will add a small sign noting the water.
2. Glueing shoes and other personal items to ceiling.
3. Saran wrapping their cars. I've done this a dozen times to friends at work, at home, on a date!; and with upwards of two dozen rolls stock piled so far, their three cars will get about 1200 sq ft of wrap each. (This is my personal favorite, I am the Wrap Master

)
4. This one is dangerous if not applied correctly!!! I know a forumla for a paste that, when dry, is very touch sensitive and will explode if even a feather touches it. I plan to put this paste on the cabinets in the kitchen, among other places. It will be on the parts where they're not able to grab to open them, so there is no risk of injury.
5. Will be adding food coloring to their milk, juice and water. Simple, but just imagine opening the fridge and seeing three gallons of milk, one red, one blue, one green. I may even put some in my own milk, just for kicks.
6. Yarn spider webs. This will cover the upper half of their door frames, above the paper cups. Yarn is really cheap.
7. Plastic utensils glued just about everywhere I can't do any of the above to...
8. Either vaseline or glycerin on their door knobs. I think glycerin might evaporate too quickly, but we will have to see.
Remeber folks, none of these should do permanent damage if applied correctly! Pranks are not ment to seriously injure, maim, blind or otherwise damage people and their belongings! If you plan correctly, your friends will just be happy its all over with and their stuff is back to normal!
Cheers,
Marty
PS. I usually don't mess with bathrooms. I do like the shower kool aid however, so I will be investigating that futher...