My signature items are clear flat marbles with one of a kind designs... You can see a picture here Link to Swag Pics
I would love feedback as to whether or not you would like to find something like this in a cache and keep it...
I would definitely keep something like this; however, I do not like finding business cards or playing cards. They take up a lot of room and don't seem to be very "fun" to keep. But that could be just me. My son loves finding army men and things like gears. My daughter loves finding charms and fairy bottles. They both love to keep pennies, nickles, dimes and foreign coins. My husband has a thing for rubber ducks LOL
Also, kids' rub-on tattoos do NOT hold up well in caches, nor do stickers. In the heat and cold they come "unstuck" from the backing and then lose their ability to stick completely.
FYI I have found "floating charms" on Amazon which are tiny enough to fit in all but the smallest of nano containers (easily fit in metal bullet caches). VERY cute and full color. You can get 50 for less than $15.00.