Lots of play money (custom-made is better).
Assortment of prizes that will be auctioned off.

If there is a concern that this is paying scouts to do good turns, then definitely don't use it. Keeping it fun, and rewarding silly things, should help with that.

This activity takes place during a long activity, such as an all-night Lock-In or a Day Camp.

All leaders are given a set amount of Scout Bucks with the task of distributing all of it to scouts.

Scouts receive Bucks by getting noticed doing something helpful or winning a game or being a good sport or singing a song or standing on their head or anything else the leader feels is worth a Buck.

Towards the end of the Lock-In, bring out the auction items. Scouts can bid on the things they want. Scouts can combine funds with buddies or as a patrol to get a more valuable item.

Collect all the Bucks to be used again next time.