A while back, I took a look at some Half-Life 2 improvement mods, and ultimately determined that the best way to play Valve's 2004 masterpiece was, well, without any mods whatsoever.
At the time, one of the mods I tried to look at for the piece was called Half-Life 2 Update, created by modder Filip Victor. It had been in the works for a while, but the move to SteamPipe broke it, and there had been little news about it since. Well, it's finally arrived as a free download on Steam.
The Update mod promises a host of visual upgrades to HL2, including detailed shadows, better interior lighting, environmental fog, particle effects, better water reflections, and more world detail. It also fixes bugs and improves scripted sequences and the collision system. The ultimate goal was to improve the look of the game without making any drastic changes along the lines of the FakeFactory's Cinematic Mod.
I downloaded it and gave it a try. It's all a bit subtle—it's not at all like playing a brand new game or anything like that—but definitely noticeable. The game does look better, and crisper. There's more detail, the shadows are definitely nicer, the water looks great, and it brings Half-Life 2 closer to the visual improvements we saw in Episodes 1 and 2.
It's not something you'll call people excitedly into the room to see, but that was never really the point, and there's only so much you can do with a decade-old game unless you want to completely overhaul it from top to bottom. I'd say, if you've been looking for an excuse to play Half-Life 2 again... well, first, who needs an excuse? It's still fun. Except for the Hoppers. The Hoppers are dumb.
Also, who wants to tiptoe over the sandy beaches again, really? And Ravenholm has kind of lost it's scariness by now. And the boss fight at the end, where the boss is basically a box you have to knock the sides off... eh, skip that bit.
But otherwise, it's a fine reason to play your favorite parts of the game again.
While Filip Victor is the developer of Update, he wasn't alone in his work. He had help from the Half-Life community, who helped him compile lists of bugs and issues. The mod also includes community commentary: select it from the main menu and you'll find nodes scattered throughout the game allowing you to listen to the musings of several YouTubers and Ross Scott, creator of the video series Freeman's Mind.
You can view a PDF of the changes and the ideas behind the mod right here. And, here's a nice comparison video that probably does a much better job of showing off the changes than my screenshots do.
Or, just download it from Steam and the next time you get a hankering for some Half-Life 2, try the Update version.