OK, this should be an easy one. I would say our rice cooker/steamer. It was Yan Can Cook brand, from a local Bay Area Chinese chef with a public TV cooking show. i figured it was good for six months, tops. We've been using it to steam broccoli on a weekly basis for a decade now. It even makes decent rice, at least for a simple non-fuzzy-logic cooker that cost next to nothing. I'm sad to get rid of it, but the nonstick coating is finally starting to wear off and I don't care to ingest teflon.
It looks like this one, but it's a 9 cup model: http://www.flickr.com/photos/tedmills/458243651/
So what's your kitchen gadget that punches way above its weight?