Best Second Hand RPG Purchase
I am a Half-Price Books hawk. I routinely drive to multiple locations to check and see if they have any good stuff. I'd have to say my best purchase was finding every single Gamma World adventure at a Half-Price Books a few years back.
Coolest Looking RPG Book
Hands down, the DCC RPG rulebook. I go back and look at this book all the time just for the artwork.
Most Complicated Rpg Owned
Well that's an easy one. Aftermath, the Post Apocalypse RPG from FGU. I'm convinced there is no way to learn this game from the book. It was taught to me by my high school GM, who had it taught to him. I'm not sure I could even run it now.
Favorite RPG no one else wants to play.
I don't have a good one for this. My players are awesome. They'll try anything a few times at least. I think the only games that died and never returned were Dark Heresy and the D&D 4E Gamma World. (Dark Heresy came back even.) I'm running a DCC rpg game but I'd kinda like to play in one. I was scheduled to play in one at a local store but it's been indefinitely postponed.