I believe many geocachers have the same tendency to collect things (other than 'Smily's'). Signature items are a fun way to leave a little reminder of your visit to the geocaches found. These items range from business cards to hand-stamped postcards, plastic toys, bottle caps, stickers, and poker chips. Some geocachers design and leave very personalized and wonderful geocoins.
Pathtags
In my experience, Pathtags are a great way to create your own personalized signature item. Many people have them produced in order to leave in geocaches; they are small enough to fit inside a 35mm film canister. They are, however, also often traded through the pathtags.com "Trade Manager" feature.
For more information, go to www.pathtags.com
I have designed and had produced several pathtags, most of which have been traded to zero.
#5968 - Mmmm....yummy cache!!
#8049 - iCache: Blue
#8643 - Threatened Species - Woodland Caribou
#10938 - iCache: SnowCaching
#11435 - Threatened Species - Polar Bear
#12644 - NPS - America's Best Idea
#23131 - USFS - The Greatest Good
One of the more easily made (and cheaper) options for a signature item was to use blank business cards purchased at the local office supply store and add my own design. My first signature card was rather simple and included what would become our signature tagline: "Mmmm...yummy cache!".