The Twist and Chop by Kuhn Rikon is a great little device. So far I have tried dicing onions and garlic with it and it has worked great. The great thing about it is that it is small, 
easy to clean and quick. I think it is much more useful than similar sized electric choppers from Cuisinart and Kitchenaid. I wouldn’t hesitate to use this, where as I might be a little reluctant to haul the others.
Since it is compact you have to pre-cut some items, but it is still quicker to quarter an onion and throw it in, than it is to dice it. I also think it works better than the piston like choppers that you push down on. Those seem to mush things up, while this devices chops them.
There are two blades in the bowl, that are attached to the base/top (the green part). When you spin the green part, the blades spin around. You can also rotate the bowl so things don’t stay at the edge away from the bowl. There is also some gearing in the green part to make the blades spin faster.
Pros:
- Compact
- Easy to clean
- Chops instead of mashing
- Fun!
Cons:
- Small bowl
- sort of pricey (but well made)
Kuhn Rikon Twist and Chop