Ever heard of geocaching? It's a game where you use your GPS to find "caches" - containers of varying sizes - that have been hidden outside all over the world. Inside the container is a log where you sign your username to show that you've found it, and also sometimes there are trade items. You can take an item out of the cache as long as you leave another item of equal or greater value. Generally the items are small toys or random dollar store items. I thought it would be fun to come up with something different to leave in the caches that I visit, so I made these amigurumi crocheted fruit keychains.
I couldn't find any keychains for sale in my area so I just ordered some online. I got 50 of them for $13.50 which was a pretty good deal.
I also made little tags out of shrink plastic (aka Shrinky Dinks) to put on the keychains with the name of the website (geocaching.com) and my username (blacked out for privacy):