Alternate Classes
These are standalone classes whose basic ideas are very close to established base classes, yet whose required alterations would be too expansive for an archetype. In this case, that's the samurai and the ninja—specifically Asian-themed classes that have long and unique histories, as well as great cultural cachet, but which are similar in concept to the established cavalier and rogue, respectively. An alternate class operates exactly as a base class, save that a character who takes a level in an alternate class can never take a level in its associated class—a samurai cannot also be a cavalier, and vice versa. The antipaladin from Advanced Player's Guide is also an alternate class.