Do you remember the awe you felt first firing up Half-Life 2 in 2004? Now fire it up in 2010. It's more like "aawwww". Flat textures, dull lighting. It's a shame! What this game needs, then, is a makeover.
A makeover like the one provided by Filip Victor. It adds HDR lighting, new models, new textures, an upgrade to the Orange Box engine (Valve performed their own tweaks for the 2007 re-release of the game on Xbox 360) and even some new Steam achievements to the ageing PC version of the original Half-Life 2.
You can see examples of the improvements made in the clip above (though be advised, you'll want to kill the sound). If you like what you see, you can find instructions on how to download the mod below.