Boxer (3.5e Alternate Class Feature)
From D&D Wiki
You have trained in the esoteric art of unarmed combat.
Replaces: If you select this class feature, you do not gain a fighter bonus feat at first level.
Benefit: Not all unarmed combatants are monks. You have developed your own body as a deadly weapon. You gain the Unarmed Strike ability of the monk. You use your Base Attack Bonus as your monk level when determining unarmed damage. Do not add the BAB derived from any class that grants unarmed damage improvements, such as the monk. Instead, add their unarmed progression to the BAB. Base unarmed damage cannot exceed 2d6 (for medium size, other sizes will match accordingly) or damage cannot exceed that of a combined BAB of 12th level.
At any level where you receive a fighter bonus feat, you may take the monk class feature Flurry of Blows instead. You may only flurry with your unarmed strike or light weapons, and the -2 attack penalty does not improve at later levels like a monk's does.
This substitution level provides a non-alignment restricted path into unarmed combat. These fighters make more appropriate bouncers and bruisers than monks.
There are several ways to calculate your effective monk level. This is so that a fighter may choose a martial prestige class and still retain a level-appropriate unarmed progression. This method does not cover all possible combination of prestige classes. Hopefully, it sufficiently covers those classes that an unarmed fighter or fighter/monk is likely to pursue.