As far as unpolished gems go, Troika's Vampire: The Masquerade -- Bloodlines could be classified as a sapphire, maybe an emerald with the 1.2 patch. With the latest unofficial update however, which now sits at version 7.9, it easily hits ruby, and perhaps even diamond, heights. Why the bizarre analogy involving precious stones? Because the game's just $US5 on Steam, that's why.
If you want to experience the wonders of Valve's Source engine before Half-Life 2 went and made it famous and what not, look no further than Bloodlines from now-defunct developer Troika. True, it was rough as guts on release and contributed to the studio's downfall, but some seven years after it hit shelves, you can now experience the RPG, based on White Wolf's popular pen-and-paper system, as it was (probably) meant to be.
To do this, you'll need to apply both the official and unofficial patches. Fortunately, you don't have to scrounge the internet looking for them; The Patches Scrolls has them conveniently located on the one page, along with some complementary mods. Users of Windows 7 64-bit will want to check out this Steam forum thread for tips on getting it to play nice with Microsoft's OS.
As I write this, there's about 16 hours and 30 minutes left on the sale, so you have a little bit of time to act. But not much. If you haven't played Bloodlines and want a heavy RPG for the weekend, you could do much, much worse*.
Image: Steam / Activision.
* Yes, Big Rigs is hardly an RPG. But then, it's barely a game.