Unarmed Fighter

[Jondor_Battlehammer]

TWF would almost be a must, since your damage will be lower than a normal fighter. You may as well double his attacks. I would also suggest Knockdown(?) from S&F. Do 10 or more damage and you get a free trip.

 

[hanniball]

I would strongly suggest skipping the Reaping Mauler levels. You can get far more impressive numbers from other classes. One of the more viable means of creating an unarmed melee combatant involves increasing your size as much as possible. This is easily done via Psychic Warrior as SlagMortar suggests, but other options are available if you're not interested in a 'caster.'

Consider a Human Fighter/Barbarian/Frenzied Berserker with the Jotunbrud feat from Races of Faerun. A monk's belt will net you 1D8 unarmed damage and wis to ac if unarmored. This gives you a 'Natural Attack' qualifying you for the Improved Natural Attack feat. This'll bump your damage up to 2D6. Tack on all the strength boosts from Rage and Frenzy, not to mention the extra attack frenzy grants you, and you'll be a formidable unarmed combatant.

However, I'm not sure which sources you're allowed to choose from or what level you're starting at, so this could be useless to you.

Either way...just my 2 cp

 

[atomn]

If you don't like the Lawful side of the Monk but want the dip into Monk to get their abilities, you can go with Battledancer from the Dragon Compendium (if your DM allows it). It's like a Monk but is geared towards Charisma instead of Wisdom.

If you are cool with being Lawful, the Justicar PrC (C. War.) is a very good grappler.