I've had some pretty shitty roommates, especially in college. My shittiest roommate, and now the reason I will never again live with another person for as long as I live, topped them all.
My former roommate was a narcissist. She was always the victim of something - ALWAYS. If I wanted some alone time (I'm an introvert and need a ton of alone time to recharge after a long day at work surrounded by people), she would pout and moan and piss her pants about me "leaving her all by herself with no company." She refused to entertain herself, and she expected me to take the time to play games with her or watch movies with her or hold obnoxious conversations with her to keep her company (e.g.: OMG DID YOU SEE WHAT SHE WAS WEARING TODAY???).
She constantly whined about her friends' wont to belittle others based on their clothing choices, but she was too blind to see that she did the same things.
When I had a girlfriend over, my roommate banged on my door when we were having sex, ruining the mood. We weren't even loud at all. She wanted company, despite her boyfriend being there at the time. Regarding sex, my roommate would brag up and down about her boyfriend having a 12 inch cock, yet she would whine, whine, whine about him lasting only 5 or 10 seconds. So whenever my then-girlfriend and I were going at it for a while, she would get jealous and interrupt our sex.
She and her boyfriend would take HOURS in the shower (each time without asking me if I needed the bathroom first), but God help me if I so much took a 10 minute shower without consulting her.
She had her boyfriend move in for a month without my consent. She got a second cat without my consent (we already had two at the time - one was hers and the other was mine. I felt that 3 cats was too much for our tiny apartment). When confronted, she simply said, "We'll see how it goes," and walked away.
She was a vegetarian and constantly talked down to me for eating meat. When asked how my eating habits affect her in any way (we had separate dishes), she pulled some excuses out of her ass. Ironically, even though she ate healthy, she was completely sedentary and did not exercise at all. She gradually gained weight while I, living an active life, did not. She took victimhood in her weight gains and often yelled at me for "staying fit".
She had a car but refused to take care of it in the winter. When she needed to brush snow off, she would throw bitch fits when I would refuse to do it for her (why should I?). When we went shopping together, she would blackmail me into sweeping the snow off her car "because I am giving you a ride." She was very manipulative.
She refused to take care of her cats. While she fed them well, she could not be bothered to consistently clean their litter boxes for months on end, despite me, neighbors, and management complaining to her. She had a previous cat who died, and I've always suspected part of the reason he died is she didn't want to maintain his litter box. She would beg me to "help" her remember to clean her cats' litter boxes, so I suggested we do it together. What I meant by this was while I clean my cat's, she cleans her cats'. Her interpretation was that I hold the bag for her while she dramatically gags and coughs and moans. "This isn't my favorite thing to do!" she would whine. "Then why the fuck did you get two cats?" I would retort. She would then cry and throw bitch fits because I wasn't supporting her.
When she graduated her MS program, she begged me to come to her graduation festivities. At the time I was suffering from severe insomnia and was not able to sleep well at all. On the morning of her event, I told her I would not be going because I wasn't feeling well. I hadn't slept at all the night before. She got pouty and suggested I rent a car. Yeah, that's a good idea. Drive a car while weary. Nothing could ever go wrong! She gave me the cold shoulder for 3 weeks and finally exploded in a visceral fireball. "YOU'RE SUPPOSED TO BE THERE FOR ME!" I mean, she only had her boyfriend, entire family, and other friends there. She really didn't need me there. Plus, she canceled coming to my MS graduation, too. I didn't retaliate against her for not coming to mine (I was genuinely not feeling well) but I explained to her that she can't get so fucking pissy with me for not going to her dumb graduation when she didn't go to mine. She ended the conversation with, "Well, you need to figure out how to make it up to me."
Finally, in true narcissistic nature, she threw the biggest bitch fit when I bought a friend (a friend that she didn't like too much) a Christmas gift. She screamed and screamed and screamed at me for 20 minutes about how dare I do a thing like that. At this point, I was already out of the friendship. I'm just sorry it took so long for me to see her true nature.
Found another apartment a few months later. She's gained a lot of weight since we parted ways. When she moved out of our previous apartment, she left THE biggest mess and graciously "gave" me all of her food - which was expired.
I have so many more stories about her, but that's the gist of her. We lived together for a year and a half. We met in college and knew each other for about 8 years.