This is my rubber band ball, measuring ten inches tall and weighing seventeen pounds as of April 2015. It's certainly no record breaker, but it makes for a neat doorstop. My brother has one too, and it was 50 pounds last time I checked. Here's a photo of our rubber band balls side by side:
These are a couple of old pictures from when the ball was eight inches tall and nine pounds.
I'll update this page if I add any more rubber bands.