A sandbell is a cross between a sandbag, a dumbbell and a kettlebell, among other things, and it allows you to perform a wide range of strength-building activities with just one tool. These sandbells from Hyper Wear are made from tough neoprene that can stand up to plenty of yanking and stretching, with weights ranging from 2 to 50 pounds. A zippered opening allows you to add (and remove) your own sand. Individual bags start at around $10 each; a complete set costs about $400. Order from Hyper Wear: www.hyperwear.com.