I'd love one OnePlus One because I'm such a hipster that all these other phones are just too main stream...but on a serious note, I'd love one just because it's an unlocked, unmolested device and I can use it on any GSM network in the states and when I travel (which I often do for work).
I'd really like a phone with a larger screen that I also don't have to root and constantly tinker with just to get OS updates. A better camera than the one I have would be cool as well. That is all.