Here is a space saving dumbbell that replaces multiple weights. The Wonder Maxi Adjustable Dumbbell is adjustable from 5 to 25lbs. It can be used to perform lunges, shrugs, curls, and raises. You can change weight in about 3 seconds. The Wonder Maxi Dumbbell has an anti-slip handle. It comes with a plastic tray for storage.
You can change weight with a push and slide. More information is available here.