Jerusalem artichokes are aces. Versatile too - you can eat them raw or cooked in any of the same ways you'd cook potatoes. Unfortunately they're a right knobbly bastard to peel. And they go brown immediately (usually half way through peeling) so you have to dunk them straight into acidulated water. Though once immersed they hold their colour well.
You can boil them in their skins and then scrape them afterwards, but if you're looking for style this method does tend to leave you with fairly grubby-looking roots. I find the best way to get bone-white knobbles is to peel them as best, and quickly, as you can using a potato peeler, dunk them in acidulated water, then finish them off using a small knife.

They're also a bit sensitive to the exact amount of cooking - going from a bit too hard to mush in very little time.
Still worth the effort though.