In no particular order, I've used fluxbox, openbox, probably a couple of other *box, xfce, lxde, lxqt, RazorQt, KDE(3.5), KDE Plasma (is that 5?), Gnome, Gnome2, Cinnamon, Unity and Enlightenment. There might well be one or two others. (I gave up on Ratpoison in about 30 seconds...)
I'm currently using Enlightenment, but the only one of those environments that I'd never use again, given the choice, is Unity. Ultimately, all the desktop environments present pretty much the same thing in slightly different ways. Am I the only one who doesn't really mind what the environment looks like, so long as it is reasonably functional?