My mom made me get rid of all my Yu-Gi-Oh cards in 2nd grade because they were too 'demonic' 
Same! Except it was Pokemon. I even had to SMASH my Pokemon Red game!
My school jumped on the bandwagon that pokemon was demonic too. I think it was just a ruse to get kids to stop bringing the games and cards to school (they couldn't bring them if they didn't have them). Some parents bought it, but luckily my mom wasn't one of them. It's especially ridiculous now that I don't believe in the supernatural at all.
I can't think of anything I regret selling because I don't sell stuff. I figure the stuff I have either isn't worth anything after I've owned it or it's not worth the trouble of finding a buyer. I'm also way too nostalgic to let go of anything. With the exception of things that have been lost or broken, I still have all the toys and video games from my childhood and my brothers' childhoods (they've kept a few things for themselves though). I have way too much crap lying around....
Mainly the things I regret not having are things that have been lost mysteriously over the years, most likely from my brothers' taking them or trashing them and not telling me.
