I'm pretty surprised that no one chimed in on what they think is a good DM map. I guess I'm a weirdo for having favorites lol.
I have a few hated maps too!
I hate the new version of Phobos in UT3 for example. It's so visually busy, that it's hard to find your target.
I'm also not a big of Quake3 dm17. The map that's suspended in mid air with the railgun on the far away island. I can't pinpoint why I find the map so annoying, but I could go the rest of my life without playing it.