Human Pinata

Wrap a leader up in duct tape with the sicky side out. Stick candy all over the tape.

Then using ropes strung around his arms & legs (or a harness if you have one, which every good leader does) hang him from a tree.

One by one, let the kids beat the candy from the leader with a pool noodle.

If you want to do it inside a building, you could do something similar to this picture I got in an e-mail titled "Redneck Timeout".