I was a summer camp staffer for many years -- fertile ground for pranks. This is a list of great ones where no one gets hurt, which is an important caveat. Your additions are welcome.
  1. Setting up the entire cafeteria on the sports field.
    This takes time and should be done in coordination with kitchen staff. This one can be done at summer camp or at small colleges with a sense of humor. PROTIP: Don't do it at UF #donttasemebro or UC Davis #pepersprayhurts
  2. Take the wheels off the camp director's golf cart
    Added bonus: putting it on blocks in the cafeteria. Down side is that you may screw up the alignment but it is worth it.
  3. Move sleeping campers out of the bunk while in their beds
    I will neither confirm or deny that I told my camper, as together with my co-counselor we moved his bunk bed outside at 2 a.m., he was dreaming and I was from outer space. 👽
  4. Plastic wrap an object
    My bed was wrapped in plastic and the filled with packing peanuts, but this can be done to a desk, an office chair, etc. But be careful, this can hurt paint and electronics.
  5. Sign your friend up for PAC emails
    While not for camp staff per se, this is a solid, low risk prank. I was recently added to every GOP presidential candidate's email list. Also, Jeb is an acronym. Who knew? ¯\_(ツ)_/¯
  6. Penny for your thoughts
    This costs between fifty cents and a dollar. Taking a roll of pennies and give them to random people and asking these pawns/collaborators to ask your target, "a penny for your thoughts?"
  7. Non-birthday birthday singing
    Easy, low risk, and can be done effectively at any mid-range restaurant where servers sing. Best opinions are cheesy Mexican joints. Extra points for a Mariachi bands.
  8. Flash mob follow someone
    Very good for large lecture hall situations or events with free admission, get a large group to shadow your target while wearing matching outfits. Singing while walking is completely optional.