They are quite wide, though - about half an inch across. This makes them uncomfortable to sit on in a back pocket.

Deal Extreme used to do thinner butane ones that were flat and roughly a quarter inch thick, eg http://www.dealextreme.com/details.dx/sku.10087 which I prefer. That one's a jet flame and not waterproof. They also do a flint ignition one that's the same thickness but wider, and which has a cap that covers the mechanism. The cap isn't sealed but is surprisingly good at keeping the water out. It also protects everything else from the grind-wheel and prevents accidental ignition or fuel leakage (as compared to a Bic with exposed mechanism).

Unfortunately the build quality isn't very high (but then the peanut rarely lights for me first time either), and there's no fuel window (again, the peanut lighter lacks that too). And DX don't seem to be shipping any butane lighters currently.