The coolest one I've seen -- someone else no doubt knows the one I mean -- is where the cellphone is hinged. It looks like a cellphone, then it opens on the side, you turn it around horizontally and it's a decent sized screen with a long width (probably the 16:9 HD dimensions) and the bottom section gives one a larger keyboard than any other portable device I've seen.
Natch, it would probably be a bit more burdensome than a regular cell because of it's size, but instead of carting around a PDA or a Blackberry or a cell with a palm-top both, it would probably be worth it.
Again though, notice, that's just for Net connectability. Still not big into playing songs on it, watching streaming TV on it or using it as a video camera either.