Community Sourced Brainstorm - Culligan Caps

I have been saving Culligan water bottle caps at my office for a while. I have about 30 of them now and they are just taking up space (not a lot of space, but..) They are off of the 5 gallon bottles that most everyone has in their office.

Other than using them for hallway hockey in the office, I need to do something with them. I am sure other people have found ways to upcycle these things into something cool and useful. I would definitely recycle them before throwing them away, but it looks like there is a neat project just waiting for these.

I have included pics of them.
1. top of cap with label.
2. bottom of cap
3. cap with BIC pen next to it to show size.

Add your suggestions to the comment box below. I will try to make something using someone's idea (if they don't mind) and post an instructable on it when finished.

The kids and I have a lot of fun building things we find on here and have uploaded our own "how to." As they get older they are more into the site than ever and want to upload more.
Thanks Instructables Community!