Fluxbox. This year. Last year. Next year. Fluxbox. Fluxbox. Fluxbox.

I use Blackbox in Windows, but it's so much better than the *NIX original that I can prefer Fluxbox under Linux.

I use XFWM. I just went to using XFCE as my go to desktop environment this year after KDE3 was starting to not be provided as an option in so many distros. I discovered a lot of themes at xfce-look.org, and even found it pretty easy to create my own XFWM theme. Check it out: Pewterburg-Gold.
As I discovered more about the window manager, I found out that only recently it has the capabilities of prelight effects for the buttons, but I really like it's versatility.

XFWM bumped since KDE4 ditched konqueror, so they get my vote this year

XFCE team! stay cool

Since I note from elsewhere that you're a fan of "rolling your own" you may want to check out OpenBOX, wh/is an awesome fast and lightweight window manager if you're willing to spend the time tweaking it to your personal tastes. I'm lazy in my old age and just go with the convenience of default Gnome these days, but back in the day when I was more into such things my OpenBOX set up was my fave ever. That was just one lean, mean, and clean desktop that did everything just the way I wanted it to w/o getting in the way. Oh, and just for reference, it replaced Fluxbox, wh/in had in turn replaced Blackbox.... Which probably goes some ways towards explaining why I am so opinionated about the idiocy that some of the HIG fascists have enforced upon us....

DWM.

Compiz looks awesome. It was also a major appeal that caused my brother to try Linux.

Enlightenment (e-17) its really looking good and very functional.

Fluxbox

I love fluxbox!

In my experience e16 and e17 are quite different

OpenBox all the way baby!!!

Openbox!

Where's Metacity? Did you know you can turn compositing on with Metacity, and then it can do many of the things compiz does, and quicker too?

MetaCity is already a listed option (6th from the top).

--jeremy