Part 3: Episode 3: TrainsEpisode 3: Trains
This time around we get introduced to a new gimmick: environmental hazards that can kill you in one shot. We also get a final look at a gimmick: environmental hazards that can kill you in one shot. We'll also never have to see pistols, SMGs or MPs ever again through the rest of the game after this level as we re-earn the assault rifle and there is literally never a point where going back to those other weapons is a good idea unless you run out of rounds for the assault rifles.
A note about weapons in this game: They come at you fast and furious. Oftentimes they come at you in a completely nonsensical order as well. By the time we get the Heavy Machine Gun we already have three or four weapons that are better and easier to kill things with. The game gives you a shotgun as you go into fights that make no sense to use a shotgun in (as seen in this video). Additionally, there's never a good reason to use some of the weapons. The pistol is basically useless, especially considering it gets outclassed by the MP in every possible way. If you don't experiment with the thing you may never find out that the game offers a completely ineffective melee attack. Ten or so hits to down a guard in the first level, and it doesn't stun them at all, so they are just firing into you as you try to beat them to death.