I have the key to my stateroom from the old Big Red Boat and the key to my room at the Buena Vista Palace. Both are from my honeymoon in 1988. I think I have my on-board credit card too.
I still have mine from 2000 around here somewhere. My most recent one from August last year has a permanent home on our sunglass holder in our car. Every time we reach up there we see them and it gives us warm fuzzies!