Dark Project 2 : The Metal Age (or better known as Thief 2)
One I bought myself, the other was a present from someone who didn't know I already had it...
Blood Omen II
Bought it for the PS2, but then found a website called thelostworlds.net which looks into development "secrets", cut content and hidden content for the Legacy of Kain series. It got me intrigued, but you need the PC version to use hacks and modded savegames to unlock that stuff. It was just a few bucks.
Pathologic
Bought the English version first, despite English not being my maternal language... I really love this game, but the translation from Russian makes Google Translate look flawless. The game is mind challenging, complicated, cryptic and full of text, so it doesn't help when every sentence is filled with godawful grammar, cryptic phrasings and wrong information. For instance, one of your characters repeadetly insists she's immune to the disease. So I went hugging infected.
Fortunately, the German version has none of that, and it's laughably cheap.
Devil May Cry 3
One for PC and one for PS2. Even with a Playstation controller, the PC port is not recommendable, though it looks sharper.
Fallout 3: Broken Steel (Xbox and PC)
Stupidly clicked around on amazon, didn't notice I was ordering the Xbox-version... Ripped open the plastic foil at home, admired the green "radioactive" case, then raged. You need Fallout 3 for it, it's opened, it's German (and may be censored and not switchable), and if you wanted it, why the hell would you play FO3 on Xbox (no mods)? Refunding is not worth the hassle, if even possible, and nobody would buy it.