Old retail job. There was one guy who was just...the biggest douchebag on the planet, regardless. But the manager had no spine and honestly just didn't want to deal with it when people complained to him, so when Douche went and whined that he wanted to be made full time (guaranteed 30+ hours a week and the option to sign up for benefits), the manager just went ahead and did it despite there being plenty of people who actually would have deserved it and, you know, didn't call off for every other shift and weren't a nightmare to work with. (We didn't have the hours to let everyone who wanted it to become full time - none of us even knew it was an option for ANYONE else to do so.)

Douche was a cashier. But when he was officially full time, he started going around to everyone who wasn't with his benefits papers and pretending to not understand them so he could thrust the papers in people's faces all, "So, I'm confused, do my benefits start now, or...blah, blah, blah," just to not-so-subtly brag that he was getting them at all. He also started to refuse to go by the title of "cashier" and instead began to refer to himself as "a customer service representative." He also began refusing to ring register, and would throw legitimate tantrums (like, with tears and stamping) if he was told he had to, because suddenly it was beneath him or whatever. He started bossing around other cashiers, that he was in no way above - full time did not make him a supervisor or anything like it, he just got a few more hours than most. He was pretty awful BEFORE the full time hours, there was no working with him at all afterward. Thankfully he wasn't around much longer after that. He got a second job, and when someone else got fired there he quit our workplace because, "Well, now I have full time hours at the other place, and it pays better." Idiot didn't take into account that the other workplace was eventually going to replace the person that got fired, and when that happened he came crawling back for re-employment but he had burned so many bridges in his last two weeks (that's another story) that it wasn't going to happen, thank god.