Half-Life 2: Episode One - 05 - Exit 17 [Hard]

Chapter 5: Exit 17
After making their way through a zombie-infested hospital, Gordon and Alyx reunite with Barney, who has successfully led a large group of Resistance fighters to the doorstep of the train station. With the Combine just a few minutes behind, our heroes must escort the last evacuees safely to the trains and catch a ride themselves before the Citadel blows, in the final chapter of Episode One.

Playlist with all completed chapters:
   • Half-Life 2: Episode One - Full Playthroug...  

Notes:
There are many supply crates hidden in the train station parking lot, I didn't show all of them (1:00)
Between escort runs, Gordon can replenish his pulse ammunition for the OSIPR by revisiting the room at 1:41 - at least one pulse round always seems to respawn in there
Gordon can man the turret that Alyx uses to defend the entrance to the loading area. Alyx will let him use it, and return to her position after he leaves (2:28)
If Gordon continues to stay in the trainyard instead of following Alyx and Barney after all the citizens have been escorted, Shotgun soldiers will start infinitely spawning, 2 at a time (11:16)
The Strider at 13:00 serves as the final boss of the game and behaves notably differently than its HL2 counterparts. It has a faster fire rate with its pulse cannon (though slightly less damaging per shot), doesn't "walk" its fire towards Gordon, and uses its Warp Cannon much more frequently to try to kill Gordon. Its Warp Cannon also doesn't seem to be as powerful, compared to the one in HL2 that took apart building walls
The metal wall panels at 15:05 WILL fall off if shot enough times by the Strider. This is to keep Gordon moving and prevent him from staying in one spot for too long

Trivia:
Barney seems to have been involved in an "altercation" with a Civil Protection officer right before Gordon and Alyx showed up (0:40)
The citizens that Gordon helps evacuate seem to be coming from a locked door behind Calhoun (3:13)
The fighter at 1:54 will continue to shoot at infinite-spawning manhacks and City scanners until all the citizens are successfully led to the trains. As Gordon makes more and more trips back to this room he will be able to observe more fighters ontop of the train
The .357 Magnum is the last weapon to be procured by Freeman in this game (2:14)
The first and only time Gordon defeats an APC with the RPG (7:15)
The last time Gordon fights Civil Protection in the HL2 saga, as well as the only time Gordon fights them in this game (9:17)
The last time Barney Calhoun is ever seen in a Half-Life game thus far (12:14). It is unknown if he and the rest of the evacuees survived the Citadel blast, although I would assume so as they had a good 5 minute headstart on Gordon and Alyx
At 18:00 a portal seems to be opening at the top of the Citadel, in a similar manner to the final chapter of HL2 where the Dark Fusion Reactor was used to try to open a portal into the Combine homeworld
The Advisors in the pods at 18:20 and 18:25 attack Gordon and Alyx again with their psychic powers
An unused animation of the Citadel visibly exploding into fragments is shown in this video, though I am unable to confirm if this is actually in the game files:
   • Unused Half Life Citadel Explosion