Go fighter straight through level 12 at least. Pick up improved unarmed strike, weapon focus, specialization, greater focus, greater specialization, and improved critical (unarmed strike). Improved grapple if you feel like it. You can branch into combat expertise for some tricks, or the PBS tree for ranged stuff, or two-weapon fighting if you're feeling spunky.
You'll have a BAB of +12, say a strength of 18. That's an attack routine of +17/+12/+7 for 1d3+6 damage each strike (unarmed strikes are light for non-monks, right?), average damage 8. You can two-weapon fight if you want, that's +15/+15/+10/+10/+5/+5 if you've picked up all the feats, and you can, because you're a fighter.
A 12th level monk attacks at +9/+9/+9/+4. Strength of maybe 14 because he has to have dex and wisdom for monk abilities; weapon focus, unarmed damage 2d6, you're looking at +12/+12/+12/+7 for 2d6+2 damage each strike, average 9.
The fighter is more likely to hit than the monk, so the fighter's average damage per round is going to end up being higher than the monk. And that's if you don't house-rule anything like making more feats in the Improved Unarmed Strike chain that up the damage die for non-monks or something. The fighter can wear armor, so at level 12 he's probably still ahead of the monk, AC-wise. If you get improved grapple you're pretty much the best grappler in the party, with a bonus of +20 or better at 12th level.
A level of barbarian ("that guy really loses his head when somebody throws a punch at him") puts your fighter-pugilist more over the top.
