My favorite too (and New Vegas). It's buggy and glitchy, it crashes and freezes... But it is just too damn enjoyable.

Alone in the Dark (the 2008 one). I love this game, but it is a little buggy. I didn't experience anywhere near as many bugs as some people seem to have, but there is one particularly bad one that I can't ever avoid. It's on that first car sequence where you are driving through a crumbling New York. Right close to the end of the level there is a part where you have to drive out of a window and jump a ways to the final section of the level. The only problem is, for whatever reason, that part of the level doesn't load when I first approach the window. It takes a few seconds. So, in order to not fail the level (if I go out the window without the level loading I just fall forever), I have to slow down, hit the window, back up, and then go back forward, hoping I was far enough ahead of the crumbling ground. Despite that, though, I love the game.

One more for Bloodlines from me. Very bad combat and unbalanced clan disciplines, and of course the infamous bugfest (most of them fixed by the unofficial patch though) yet this game gave me the most fun and memorable -even if not the deepest- PC RPG experience I've ever had.

I see to be lucky, Metro 2033 is the worst I've had until now. I remember encountering at least one game-breaking bug en several other smaller things, not game-breaking, but annoying: I think it was in the level 'Depot' or around, when you're alone on that car, first of all the train went far to slow in my opinion and then there was one of those mutants, on the train car thingy that just wouldn't die. In the and, the car crashed in rubble or so, and the mutant just continued making noise, sitting on that car...

Other than that, the game was very good, it was one of the most atmospheric fps that I have played.

Arcanum is a notorious bug fest and has a massive fan patch.

I never really noticed anything either, but I think it depends on which type of character you make and the choices you make. Since Arcanum is so varied, people's experiences with bugs will also be varied.

Personally, I think Divine Divinity is far more blatantly broken than Arcanum was (but I still enjoyed it immensely).

Anything by Troika and Obsidian

Arcanum before the fan patch was a huge mess. And yeah, Alpha Protocol for all the flak that it got for being buggy, when I played it I didn't encounter a single problem (apart from the spinning camera, but that was gone after 10 seconds of .ini editing).

Alpha Protocol

Buggy like crazy, but a great story and awesome modern RPG.

Pathologic. "Broken" translation and numerous bugs, but I loved it.

Also, Fallout 2 pre-patch. Started a new game two times, each time encountering the same game-breaking bug at the end of the first main quest. Couldn't get enough of it, and was relieved when the much-needed patch was released.

Pirates of the Caribbean aka Sea Dogs 2 (you know the one).

This game was rushed, force fed PotC inspired storyline and had major and minor bugs everywhere, but damn did I enjoy the ship combat. Other parts of the game were OK, and all in all it was a great game for me.