When a deck gets old, I'll try to make some new gimmicks with the discarded tuck and cards. The discarded tuck is also very useful for repairing worn-down gimmicks.
I use my playing cards to make stands for other decks. I use complicated card stacking techniques to do so, no glue or tape.
During COVID, the friends I had in my “bubble” loved it if I built miniature escape rooms for them. I built a whole story around the corrupted Monarchs, using the Monarch cards as clues once they just wouldn’t do the sleights I needed them to anymore. I also hide things in my card boxes, like a key to my lock box. Nobody suspects it because who’s going to check all of the 40+ decks?
This one’s an interesting one! I’d wondered what you were supposed to do once you were finished with cards, but apparently it’s different for everyone!