Bear Crawls and Crab walks are ok.

A few exercises I like to use for Tabata exercises, or any time, are burpees, box jumps, jump rope, resistance bands for my shoulders.

A varitation for crunches on the ab ball is position your self on the ab ball almost directly under a heavy bag. (has to be a shorter heavy bag so you can fit under it) and when you do your crunches, every time you come up you have to push the heavy bag with either arm or however you like. Once you get it going you can stop it or push it, just make it up as you go along ya know.