I love using a medicine ball at the gym and if you haven't tried incorporating them into your workout, you should. It's a great and fun way to work with a partner as well as a great way to really change up your normal routine.
Power Med-Balls ($12.95-99.95) are a great option for your home gym. These rubber balls are durable, weather-resistant and available in 11 weight sizes from 2 lbs. to 30 lbs. The balls are designed to bounce and they're ideal for partner and wall-related exercises. The 2 lb. and 4 lb. balls are the size of a volleyball. The 6 lb. and 8 lb. balls are the size of a basketball and the 10 lb. to 30 lb. balls are slightly larger than a basketball.
I like to incorporate medicine balls into a lot of my already challenging fitness exercises for added resistance. For example, try doing full sit-ups with a medicine ball overhead. It's tough! Or try having a friend bounce the ball for you to catch while you're balancing on a bosu, then you bounce it back. Not too easy, but fun! Buy them from Power Systems online.