A working CD system, for me. I have a broken add-on as well as a broken Duo. Awesome. At one time, I owned 2 working add-ons. I sold one to a buddy and kept the other for about a year before falling on hard times and ending up selling it. I've had a stack of CD games that I've been slowly amassing locally (yard sales, thrift stores, etc.) including some real gems but they just sit there, for now. I believe this year I'll break down and buy a Duo-RX but I also wanna see if someone can fix up my US Duo, just because it deserves to not be broken. It's too pretty!
As for games, I lack all the usual suspects that go for top dollar, but Bonk 3 is certainly the one I'm most interested in playing of the bunch.