Poldiac, hands down, is my personal favorite.
you can get them from mmvapors. They're pricey, but awesome.
I can't speak to the quality of anything Mark Bugs, but if you wanna spend a serious bit of coin, check out Wizards Apprentice or any of the Mark Bugs line. They are mechanicals with touch sensors, and are kind of nifty if money is no object.
If you're looking for something smaller, a GP Piccolo or a BaGua (with magnets) , or any 14500 Super T device will definitely do the trick. They're all great.