Either that, or use the Gigantic Weapon feat from the Netbook of Feats as has been mentioned. It specifically allows with proper training the use of a weapon two sizes larger than the creature as long as it is wielded two handed.
Combine that with two-handed power strike from Quintessential Fighter that allows you to increase your damage with heavy two handed weapons and you are getting somewhere..
Combine the above with the Heavy weapon rules in Magic of Faerun and make you an extremely dense 80 pound great sword and go deliver a pounding.
If you get a 26 strength (after raging) barbarian using this combination, he'll be swinging 4d6+16 damage per hit. Or 20-40 damage per hit, no save.
Erg, of course it doesn't have a save, it just felt necessary to say that after putting so many numbers next to a melee swing that is easily repeatable all day long----provided you don't mind looking like a linebacker on steroids after swinging around an 80 pound sword for more than 5 rounds.
This is of course to either a) excite you to the possibilities of high fantasy extra ordinary heroic gaming, or b) warn you away from the consequences of such feats for the more grim and gritty, low-power gamers.