Well the first three/four levels are nothing special, but after you finish the first set they get a lot better. especially the expansion pack levels are pure awesomeness (except the boss battle)

So far: Hell. As people have said, the idea and look is awesome.
not sure what was up with the boss battle though... should killing lucifer be that easy, or did i get bugged?
The change to the expansion pack has been pretty jarring though.... why are all these kids tougher than any of the enemies in the first game?

Like almost everyone else here my favorite is Hell, but after that I like the Asylum. The combination of the map design, the atmosphere, and the enemies just made it very memorable for me.

Definitely Asylum. Not very extensive but extremely atmosphere location

Hmmm... From the base game, it's probably the "Train station". There's some amazing attention to detail there... However, I like the music of the "Palace" level the most, especially the peaceful one.
From the expansion, it's Stalingrad. Interesting choice of music (the battle one)+well thought out (in this case, devastated) surroundings+need for tactical warfare=WIN.

Babel! I just love the whole climb.

I loved the level where everything was like stopped in time in the middle of wars through time. It's been a while since I beat it so I don't remember the name of the level.

wasn't that the last one? the battle against lucifer?

Yeah, and it was AWESOME! The level itself, the battle was so-so.

Awww...so much good levels.
I would say Babel for painkiller, and the city for booh...
But frankly almost every level of that game is a pure jewel, some because of the architecture, some because of the gameplay, some because of the atmosphere...it's so hard to choose one.

To mention one that hasn't been listed, Docks. Very finely crafted map that you can't truly appreciate until you go after the secrets. Although that one holy relic on the side of the building proved to be a bit problematic as it could be knocked off, taking the secret area out of the equation in the process.

I only just finished the cemetery, so I can't claim a favorite level yet, but this game is all kinds of awesome! It might make an fps-convert of me. I usually avoid these games because I have lousy twitch reflexes, and (paradoxically) I get bored. Not with this!

That's a hard decision. For 34 levels, it's very hard to choose, so I'd have to go with a toss up between The Village, The Cathedral, and the Palace. Just the design on those levels alone is awesome.

But like I said, hard to choose.

I enjoyed the Asylum level. Play it on halloween night!