The Book of Weeaboo Fightan Magic
Sometimes called Tome of Battle: Nine Euphemisms for My Dick, The Book of Weeaboo Fightan Magic is the nickname given to The Tome of Battle: The Book of Nine Swords, one of the more famous (or infamous) Dungeons & Dragons 3rd Edition (3.5) splatbooks. It introduced three new classes, Crusader (baby's first paladin, for the gamer who wanted to stab shit instead of playing support), Swordsage (which is probably the biggest source of the book's reputation), and Warblade, (which is, essentially, the fighter only comically better in every way) and a wide variety of abilities referred to as Stances and Maneuvers, which basically function as spell-substitutes for martial characters. This was supposed to lessen the power gap between martial and magical characters, which had the unfortunate side-effect of rendering all existing fighting classes kind of irrelevant. Whether this is the fault of the authors or of the system they were working in is debatable. Either way, gee, thanks Monte Cook!
Opinion is divided on the quality of the content of the book itself. Some believe the Stances and Maneuvers systems are interesting and worthy additions to the game, whereas others consider them to be bizarre and illogical, comparing them to some of the ridiculous techniques seen in Japanese anime and manga. This comparison is what resulted in the book being assigned its nickname, which has indeed become so pervasive that even many who like the content call it Weeaboo Fightan Magic.
If you're a Pathfinder player, then Dreamscarred Press has ported Tome of Battle to Pathfinder, under the name of Path of War. Included in it are six classes- Warlord (Better Cavalier with no mount), Warder (Better Paladin with no alignment restrictions), and Stalker (Ninja done right). Path of War: Expanded brings in Harbinger (Fear-based debuffer), Mystic (sort of a sorcerer/Crusader hybrid) and the Zealot (TOUGH dudes who hook into the psionics system that Dreamscarred Press also ported).