ya know, I have a GF grill too and hardly ever use it. Lately I'm much more likely to use it as a panini press than a grill. It makes a good sandwich - and the clean up is much easier than if I were grilling meat or veggies. But I don't use it enough to justify all of the room it takes up, so it would rate very high on my "useless" list.
Lately my favorite has been my Calphalon santoku knives. I'd been using the same cheap set of knives I got from my mom when I moved out on my own (nearly 10 years ago). I'm still in awe of how a good knife works.
Another "can't live without" favorite, are good rubber scrapers. I use them ALL the time!