The Metolius Freenut is a "nut tool," which is at least twice redundant in my admittedly limited and gutter-friendly lexicon. Crotch jokes aside, it's something every climber should have on their rack unless they like leaving behind $70 cams for the next guy to extract.
The Freenut has a mushroomed end to smash in frustration without bloodying your palm, and a built in clip to save a 'biner. The curve allows you to more easily get behind a difficult piece, and that's not a crotch joke, I swear. Other than that, not much else to say. It's a simple but useful tool, much like my climbing partner.