So, in preparatin for the upcoming release of Ep. 2, I've replayed HL2 and Ep. 1 over the past few days.
Highway 17 is still hands-down my favorite level of either game. I always become obsessed with cleaning up the dirty streets, and dub myself the Highway 17 Beautification Committee. Litterbugs will be shot!
I'm also still fond of the Entanglement level, because the game sees fit to give you dozens of friendly turrets you can bring with you. Except into the end-level portal :'(. Srsly, on my first playthrough, I tried to drag the turret with me into the portal, and the gate closed and separated us, and it finally fell, and I was like "NOOOOOOOO!" One of the most heartbreaking moments in videogame history.
I wish there were an easy cheat to get the super gravity gun for the entire game. As it stands, the only way I know to get it is to warp to the last level of the game, acquire the SGG, and warp back to the first level and cheat yourself the gravity gun, which will be rendered super or something.
My favorite parts in Ep. 1 are the last bit in the zombie area where it's uber dark (whee survival horror!) and the escort mission. Of course, playing through it the second time I made heavy use of the box of infinite rockets, so it was slightly unfair to the Combine. I was also fond of the dark reactor core, since I could throw people's bodies into it (hooray for morbidity!)