Munchkining is the pathological form of power gaming, where you try to "win D&D" at the expense of everyone else at the table. Power gaming can be done in a way that improves everyone's fun, but a munchkin is a jerk by definition.
True. Although munchkins can be very entertaining to
read about. See "Harry Potter and the Natural 20," starring a hilarious munchkin who lampshades the non-munchkin tendencies of his friends.
'Another peculiarity in these people was the inordinate amount of down time they required. Milo had to spend eight hours sleeping and an hour memorizing spells, but that left fifteen hours a day to put to use attending class, fighting monsters, and crafting items off-screen. Milo knew an Artificer by the name of Alton who, when he finally got his hands on a Ring of Sustenance, spent two hours sleeping, eight hours crafting magic items (the maximum amount per day) and the other fourteen hours in a day mass-producing baskets to fund his adventuring. Alton did that every day for three hundred years straight, with breaks to fight monsters to recover lost Experience Points, until he'd amassed a fortune large enough to attract the attention of a wandering Blue Dragon. Alton's unfortunate demise aside, it was just good sense to put their hours to use—they were only given twenty-four in a day, after all. And besides, manual labour was the sort of thing done during a timeskip, anyways, it's not like it got in the way of the story. Even Hermione seemed shocked by the amount of time he spent reading and working. In just one week, Milo managed to custom-tailor his fifth-hand Hogwarts uniform (untrained, but with +2 for masterwork tools (which Milo also made himself) and +4 from his Intelligence) until it rivalled Draco's in quality, read more books than any of his classmates (save Hermione) could in a year, and carve holy symbols of Pelor, Heironeous, St. Cuthbert, and Boccob into key locations around Gryffindor Tower.
That had earned him some strange looks, despite the fact that the residents there were
fully aware that there were vampires on the same continent as them. That was all in addition to the daily chores all first year Gryffindors were required to do as punishment for trying to kill or maim the Slytherins back in September. Milo theorized that, while he had to spend an hour poring over his spellbook, performing arcane research, and memorizing spells every morning, the Wizards here had to spend at four to eight hours a day (judging by comparisons between Hermione and Ron, it was an amount of time equal to eight minus their Intelligence Bonus, in hours per day) sitting around on armchairs and talking about the weather.'