While it's not a remake of Silent Hill, the Alchemilla mod drags tons of the game's atmosphere, dread, and overall creepiness into Half-Life 2. There's an abandoned hospital full of locked doors, darkened hallways, foreboding sounds, and hellish imagery to explore, if you've got the nerve.
This mod is an adventure game: there's no guns, melee combat, or monsters to fight. Explore, glean information from notes and messages, find missing keys and tools, and solve puzzles as you make your way through a multilevel hospital that becomes progressively more creepy and disturbing as you go.
The mod looks great: yet another fine use of the Source Engine that makes you forget you're using the Source Engine. The environments are wonderfully detailed, spooky, and dripping with dread (and sometimes blood). Occasionally a bit of Half-Life 2 shows up, but for the most part it's an complete transformation.
The puzzles are of the sort we're familiar with. A flooded basement needs draining before the power can be turned on, but there's a valve missing. There's a keypad on a door: scour the building for a code written in a note, or solve a number puzzle to learn the answer. Locked doors are common and keys can be gathered by careful searching or solving more puzzles. Despite their familiarity, the puzzles are still mostly fun and challenging, and they all involve creeping through the rooms and corridors looking for clues and bracing yourself for scares.
There's plenty of tension and dread. Some of it is subtle: a sound from behind a door or around a corner, a spooky operating room, the creak of a restroom stall door as you open it. Sometimes the horror is a bit more obvious, in the form of corpses or gore splattered on the walls. Knowing there's no monsters to fight seems like it should defuse some of the spookiness, but it really doesn't. I spent most of my time convinced there'd be something horrible waiting for me behind the next door. There are a couple instances where you can die, so make sure to save your game every now and then.
This mod is obviously aimed at Silent Hill fans, but I never played much Silent Hill and I still enjoyed it. I think if you're a fan of horror in general there's plenty to enjoy in the few hours it takes to play.
You can download Alchemilla at moddb.com. It comes with it's own installer, and after restarting Steam you'll see it in your game library.