Office Complex
Anomalous Materials because i like to walk around and just watching
Surface Tension and Inbound.
Questionable Ethics.
I really liked Surface Tension. Also, Apprehension.
Surface Tension and Inbound… in that order!
Unforeseen Consequences, it just creep me out for first time.
Questionable Ethics.
This is by far the greatest chapter. For me it symbolises a huge turning point in the game, when Freeman realises that the aliens are not a recent visitor to Earth, and begins to understand why the military are so eager to clear everything up. It’s also the final rest stop before the marathon Surface Tension.
It’s also the most sciency area, with high tech labs, computers and the delightful surgery room. The Tau Cannon resides here, and picking it up triggers one of the best songs of the game.
Combat is perfect in the chapter, with fast paced indoor shootouts and plenty of explosions. And who can forget the iconic laser puzzle?
It’s also the most logical level, where everything appears organised and appropriate, unlike some of Half Life’s areas. (Residue Processing and Forget About Freeman)
The first encounter with the agrunt freaked me out. I remember thinking “Boy, i really hope that thing can’t get outOH SHI-”…
why aren’t we posting HL2 chapters too?
HL2: definitely Route Kanal
Ep1: Either Urban Flight or Hospitality
Ep2: This Vortal Coil
…Hospitality?
HL2: Follow Freeman
Ep1: Undue alarm
Ep2: This Vortal Coil
the road bit in hl2
dont remember much about ep 1 or 2
City 17. I absolutely loved the atmosphere when I walked out of the terminal. First thing I looked at, as you can imagine, was that giant black dil- I mean the Citadel in the back.
For HL2, I’d say Follow Freeman. I love the strider battle at the end specifically.
For Episode 1, probably Urban Flight.
For Episode 2, I’ve always been partial to Under the Radar and the inn ambush.
Surface Tension. That was the point where I really couldn’t believe how amazing Half-Life was.
My favorites chapters is:
Inbound, Anomalous Materials, Lambda Core (<3)
What?! Nobody’s favorite chapter is Interloper?
Not that it’s mine, but still.
HL1 - the transformation between Anomalous Materials and Unforeseen Consequences is awesome. Blast Pit is great overall, and I love the huge fan room. And Interloper is enjoyable when you picture the ambient sound effects (yes, picture the sounds :-D) and constant “whooshing” while in the “outdoor” section of Xen.
HL2 - Route Kanal is pretty neat, it’s nice fighting the basic Civil Protection since a few headshots from the pistol makes them ragdoll all over the place. Ravenholm has excellent atmosphere, and as much as I hate the fast zombies, it’s definitely an edge-of-your-seat part of the game.
Haven’t played EP1 or EP2 since the initial playthrough upon their release, so I can’t offer much there 
HL1 - As the last one, the shift from “Anomalous Materials” to “Unforssen Consequences” is fantastic; replaing the level with a totally different look. I hope they get that feeling right in the mod… Also, I love Blast Pit, Questionable Ethics, Surface Tension and Apprehension (more the concept than the level itself), in that order. Hell, I love most of the chapters. I hope Interloper, Xen and subsequent chapters become the best for me in the mod, because the concept was wonderful, but the gameplay was pretty lame.
HL2 - From the very start to you arriving at Kleiner’s (Point Insertion). I just loved the atmoshpere in that area; the Orwellian city before the rebellion was much more interesting for me than the wrecked City 17 you see later in the game. I just hoped that part was much larger… but you just cannot extend what basically was a sight-seeing tour, can you? It didn’t have an interesting gameplay, and it’d grow boring if it was larger. I guess sometimes small is better. Just as in Portal. Well, I also loved the prison and Depot levels (Sandtraps + Nova Prospekt + Entanglement). Ravenholm and Highway 17 were really impressive too the first time, but after that it got too predictable and you didn’t just get the same tenssion. I’d love to go back to 2004…
EP1 - Comparing to the other HL games, I didn’t really like this. Anyway, I guess Undue Alarm and Direct Intervention were the best. It was a different Citadel; just as with the Black Mesa incident, the possibility to go back and see the citadel totally wrecked… is great, even though you don’t visit exactly the same places (and thank god; the quality of the citadel maps were MUCH better in EP1). I loved those for the story implications too; the others were just filler. Actually, from then on, it really went down and down for me… the last chapter, Exit 17, had an interesting new concept for the saga, though (rescuing citizens and a scripted but thrilling Strider battle).
EP2 - This Vortal Coil and Freeman Pontifex were really good levels, mainly because of the awesome Vortigaunts – both their script and the new gameplay along them and the antlions. The rest of the game was really good too (much more so than any EP1 level and a lot from HL and HL2), but the next best part was the ending. Oh, the ending… T-Minus One, I mean; the non-gameplay-active ending. The strider battle was great, though.
I loved Office Complex and We’ve Got Hostiles,
I didn’t seem to like the last level though.
This is also one of my favourite chapters because of the creepy atmosphere when you get out of the elevator… The cut electrical cord scared the hell out of me the first time I was going towards the vent. Inbound… Gosh, it’s so… beautiful isn’t the right word is it? Anyway, I also love this chapter because it takes me back to when I first played the game for real… <3 