If you want claustrofobic/scary play Doom3 instead of HL if you havent already.

My choice of maps are : futuristic + detailed + atmospheric

For HL1DM I enjoyed large open maps, because the gameplay promoted such spaces. The tau, rpg, and insta-hit crossbow lent to some really good long distance fighting and covering long distances fairly quickly.

Ironically, HL2DM is alot slower and I find myself enjoying smaller corridor based maps much more than open maps. Right now, Lockdown is my favorite map. Lockdown seems to have a very good balance of tight spaces vs open spaces and pockets of health/weapons to move between. In Lockdown, I very quickly developed a pattern of item gathering and movement; where I was often 'barely' getting to my next stash. The pacing seems just right.

I hated Overwatch at first. It's still not my favorite, but one thing it HAS done, is really push me to use the hand grenades, and Gravity Gun together. The fun I find in that map, is trying to knock down RPG campers, from the street.

Because I'm a big-time camper in DM, I like Overwatch for the rocket ownage. It's quite fun in Teamplay getting your team up the roof and guarding the stairwell. Now that I think about it, the layout of that map is ingenius. Each area, except for the street (worst part of the map), has its own weapon set: the basement is physics and Overwatch rifles, the middle floor shotguns, sub-machine guns and some physics, the top floor grenades and of course, rockets. There are many, many tense and active areas, but no effectively campable chokes. That the rocket position is so vulnerable is also a cool thing: the player with the rocket dominates for a time, but as soon as he runs out of ammo or somebody with a grenade-equipped sub-machine gun or magnum approaches him, he's done. The fact that the hotel in the center can be approached from any angle is also pretty innovative, though the gameplay in the street and the placement of the magnum are unfortunate.

I <3 Overwatch.