I often get sore from one I haven't done in a while. How about these two?
Stirring the pot - Elbows go on top of the ball and feet out behind you so you're in a plank position on the ball. Keeping your core still, use your elbows to move the ball in one direction and then go the opposite direction.
Dynamic hold - Same position as earlier except your hands are on the ball this time. Try to maintain a neutral spine and hold. If it's too easy, you could alternate lifting legs.
Ok, I THOUGHT the core class I did was just "ok", but judging from how my abs feel today, I guess it was really good!
Do your hands get sweaty or do your wrists get tired? I love that move but those stop me (lol, though you don't have old wrists).
What boot camp class did you do?