Was in a 4 person Suite with 2 guys I didn't really know, and one guy I was a casual acquaintance of, but hadn't intentionally roomed with - none of us had bothered to find roommates, and just wound up where we wound up.
By the end of the year, I wanted to kill the casual acquaintance every time I interacted with him.
First time all four of us met, casual acquaintance decided to talk about things we should buy for the suite. Me and another guy had both brought a bunch of kitchen supplies - cookware, dishes, etc. He starts saying all these things he thinks we should get - trash can, bathmat, whatever. Doesn't offer to buy any of these things, and seems perturbed that none of us are offering, leading to a good ten minute period where he just keeps suggesting items and staring at us like, "Well who's going to buy this?" He had brought nothing. I brought a TV and set it up in the common area.
Within a week, I came home and he informed me he had just reorganized the kitchen. Me and the other guy had intentionally kept our stuff separate, because it would be easier when we inevitably moved out - it meant there was some redundancy. So everything was now mixed together, but it was how HE liked it. He still had not contributed to the kitchen setup.
Next week I've made a lasagna that I'm slowly working my way through. He decides he wants to make Shepherd's Pie. He decides he needs the pan my lasagna is in. We didn't really have any tupperware, and I was using the pan for storage. Now, if he'd offered to go buy something to put my leftovers in so he could use the pan, that's fine. I guess I should be glad he just didn't throw it out without asking. Instead, I get the joy of him asking twice a day for the next few days if he can use the pan. Delight. Finally, I finish, and he makes his damn Sherpherds Pie. Side note: I hate Sherpherds Pie. He's super proud of his ability to layer instant mashed potatoes, corn, and ground beef, and spends about an hour taking pictures of the damn thing for Instagram or some shit. Then he eats some, and proceeds to freeze the rest in the pan. Needless to say, I was expected to wait for him to work his way through it, which I suppose is fair, but I was eating Lasagna every day, while he was getting it out a little at a time.
I owned a few board games. I kept them in my closet.
One day he wanders into my bedroom (I shared a bedroom with the the guy who hadn't brought anything kitchen related, but also wasn't a pain in the ass). He starts asking if he could look at one of my board games. Not play. Look at. Now, this isn't necessarily an unreasonable request except A. I hadn't opened the game yet, as I hadn't had a chance to play it since I'd purchased it, so there was a fairly strong implication that he was snooping around my closet, and B. It was a game I knew he had played before, because we'd played someone else's copy together before (which was the incident by which we became casual acquaintances). Again, he didn't want to play, he wanted to open it up and mess around with the pieces. I sad no. He said, "But why not?" like every whiny five year old you've ever babysat.
By this point, I was avoiding interacting with him if at all possible, and for the most part, it worked. Eventually, his roommate proper got sick of his nonsense and punched him in the face, which was fun and vaguely cathartic.