I just picked up a Torsonator from Australian Kettlebells. I saw a couple of elite strength guys using it on Youtube, so I had a play around with it at KA.
I just had a session with it, and it blasts the core like no other BB exercise. The fact you still use a plate loaded BB in a swivel that allows 360 degree rotation makes it extremely useful.
Using one arm at a time blasts the core. I'll be putting all my clients through it tonight, but so far Nina and I reckon its an absolute winner.
To give you an idea, I can do 1 arm Superman pushups, I can do superman pushups with a 20kg plate on my bum, so my core is strong, and this really challenged me.
I have a few clients off here, I'll get them to reply to this thread once theyve used it.