Missing a couple of DEs and some of those aren't even DEs.
Pantheon, Deepin, EDE, Sugar, Hawaii, ROX, Trinity (aka KDE 3.5), GNUstep...
Some of them probably next to nobody uses, but some of them look very neat (I have always liked how Deepin and Hawaii looked, but Pantheon DE is also nice) and have a fair amount of users.
If I had to pick a DE specifically, I would probably go XFCE, but LXQT looks really interesting and there are some things about the QT framework that I like. I'm really waiting on LXQT to see what applications they are going to pick up because sometimes I'm really tempted to try for that mythical lightweight QT desktop. Most of my applications that I currently use are GTK though. My preference towards XFCE is pretty much: not heavy like kde/gnome, looks really decent without too many wtf moments, cycling wallpapers, and feels about right.
I didn't really like how gnome went at all, and I've tried kde a couple of times. KDE is just kind of strange. I would get it and be like "ALRIGHT, time to try full KDE" and then customize it to mostly how I wanted stuff...but sometimes I had to make compromises for the strangest things. Like how I can't manually change the size of the clock to show all the numbers when the panel is slim or how some of the widgets that I dragged around went offscreen or something and I could never get them back. They were running...just not where I could see them. Pretty much, I felt that KDE looked pretty nice, but I wasn't utilizing any of the features specific to KDE despite having it use more resources. Some of them I don't even like (Activities). Funnily enough, I have a post on my blog about
my KDE experience...
I tried to use Enlightenment18 rather recently...but for some reason the LiveCD that I tried (forgot if it was Elive or Bodhi) just seemed to have issues with Chromium...or maybe it was flash. Configuring everything was also kind of wonky since everything seemed to spawn a new config window with a bunch of tabs to flick through...and the menu didn't look customizable. It doesn't look bad, but I can't really say it looks amazing either since you still need to have GTK/QT on top of Enlightenment, all three of which look fairly different from one another.
Mainly I hover around Openbox or Awesome and don't bother with a DE. Compton deals with my compositor wants well enough, although I wouldn't mind having some better transitions that compiz or kwin have...not that I want to use either of them. Compiz is apparently not maintained all that well...and standalone kwin is a strange setup that apparently IS possible...Not that I want to do it.