Station 51 is a single player mod for Half-Life 2: Episode 2. You are on the run from the Combine closing in on your outpost. Can you escape?
Excellent layout and splendid attention to detail, Station 51 is a nice, short romp through familiar locals with a nice touch of decay and secrets to find.
The combat is quite tight and the enemy placement is sensible. While it ended too quickly for me, I believe the pacing made it more worthwhile, and seeing your objective from afar in the last level is something not a lot of HL2 mods do :)
Give this mod a gander, it's a blast!