In terms of heavy balls, I got some bean bags that were quite large and weighed a few pounds each that worked quite well. I also made heavy tennis balls, but I used a syringe to inject water w/some waterbed chemicals into them. They looked like normal tennis balls, because the holes would reseal themselves within 3 or 4 minutes after I was done. By filling them only about 2/3 to 3/4 of the way I was able to get some nifty tricks going where the ball would wobble in the air if I spun it to get the water to slosh around inside the ball while it was in the air.

I don’t juggle very often, but now and again I will do so at the gym. They have some small medicine balls that are between 1 and 6 pounds that really give you a good workout.

Do you juggle clubs at all? It’s pretty easy to get the weight up using hammers and things like that, and you tend to get a better grip and wrist workout with clubs than with balls.