We got our principal to let a student make an ice cream sundae on her head. We bought canned whipped topping, chocolate sauce, and cherries! We held a drawing to see who got to make the sundae.
Depending on the type of fund raiser you are doing...we gave each classroom 10% of what they raised to spend on what they as a group decided. The teachers loved it - good math lesson (percents and what your money will buy) incorporated and the class has to agree on what to spend the money on. The results were everything from ice cream parties to buying a tree for the school property - to come back to as adults ... this came from a class of first grade students! Every class made smart spending decisions and appreciated the PTO's trust that they'd spend the money wisely! We used this incentive with our spellathon - it doubled the amount raised than the kids EVER brought in.
This isn't crazy, but one incentive we use for our major fundraiser is the top sellers get a limo ride and lunch at a nice restarant. They have alot of fun and you better believe that the kids left behind sure watch when we leave and come back...
Our principal had to climb to the top of the ladder of a fire truck if the kids read so many books. You may somehow be able to work this into a fundraiser too. Good luck.
At work, one of our bosses agreed to sleep overnight on the roof of the building if her sales people reached a goal. I'll bet the kids would LOVE it if the principal had to sleep on the roof--or one of the favorite, or goofiest teachers!