Using Oversized Weapons

[Cieyrin]

CWar has the Maul which is the bludgeoning equivalent of a bastard sword (ie 2handed martial or 1handed exotic), for 1D10 x3 crit

Marginally better than a greatclub.

Not quite the equivalent of a bastard sword, as it doesn't have the 1-handed exotic clause, it's Martial 2-handed only. It is better than a greatclub, though, as it has the x3 crit. It is in Complete Warrior, as Kylarra said, same as the warmace and dire pick, which are the bastard sword equivalents.

EDIT:

Half giants from the Expanded Psionics Handbook have powerful build, and in their description I believe it says the ability stacks with all other effects that let you wield bigger weapons.

I'd go with proficiency with a maul. Just out of curiosity why are you ruling out monkey grip?

Half Giants still have Powerful Build, which doesn't stack with the armbands.

As for no Monkey Grip, he doesn't want the attack penalty, which was why he ruled it out.