While people are probably not surprised I feel this way, it's definitely a pretty big thing to me. Basically, when it comes to video games, movies (on DVD, Blu-ray, etc.), music CDs, and what not, I MUST see them in their original case unless being played. Once the media is finished, I NEVER want to see it left in the device that plays it. I feel the need to keep everything on a shelf, in alphabetical order, when not used.
To better explain this, one (if not the biggest) pet peeve of mine is when I go over to someone's place and check out their games. I look inside LittleBigPlanet case for an example, but I see a copy of Resistance 2 inside. Whenever I see that, I feel like something just died inside of me. I just see it as a sin to put things back in the incorrect case. There were times where I searched through all my friends media, making sure everything goes back in the original cases. Seriously, I don't understand how people can put things back in a different case (unless they lost it). I figure if someone has the energy to put something back in a case, it should go back in the RIGHT one.
I also HIGHLY dislike it when someone leaves DVDs, CDs, games, etc. out a case and have them stacked on top of a table. That can get a disc scratched, all dusty, and so on. I use to hate how my sister did that, so I would put everything back in the correct case so I'd feel better. Laying media on the floor is even worse, but thankfully I rarely see anyone do that.
I also hate the idea of leaving games in a console (same thing with leaving a DVD in a player). If I moved the device, the disc could shake around, get scratched up for being moved, or it could autostart with it (plus you don't always know if something is inside of it. I next to never leave media in a device because I feel when its not being played, it should be placed back in the proper case.
While this somewhat relates to the topic, I'm also very anal on wanting EVERY single video game complete (unless its an old cartridge). Missing any item drives me crazy because it ruins the look of my collection. I even more so hate it when something does NOT come in its original case (such as Xbox games in a black Blockbuster case, PS3 games in a black GS case, etc.). I have drove around to SEVERAL GameStop locations before looking for a complete copy of a game. I rarely order online unless I know exactly what I'm getting because having a complete copy is very important.
Oh well, this is just another one of my OCDs. Anyone else really care about their media remaining in their respective cases when not being used? The ONLY exception I have is when I travel, where I'll carry games in a UMD case, DVD wallet, etc.