Real bingo! Right before my first cruise, I heard they had bingo on the ship. I was so excited I brought all my lucky dobbers. It was so disapointing to find they had only a game or two before a show and it didn't require my lucky dobbers.
A volume knob in the cabin for those lovely art auction announcements and spa specials. Enough said.
A few message boards located around the ship to notify freinds and family of scheduled get togethers. You know? When you go camping, you write a note for your friends on a paper plate and pin it on the sign??? When you sail with a large group, it would make things a bit easier to communicate.
I would like to see the comeback of one or more NON SMOKING ships. Really is a pet peeve of mine, but I guess it will never happen.
Somebody mentioned clocks. Good idea, especially out by the pool area.
Pilates classes would be nice (last ship didn't have any).
A roller skating rink!