Is there any reason someone would take any other weapon?
Greatsword: Twice as likely to do a critical hit, but a crit still does enough damage to reliably take most opponents out of the fight. Can be bought as an Akbitanan weapon.
Tulwar: As greatsword, but even more likely to critical.
Pollaxe: More effective against heavily armoured opponents, particularly if the wielder's Strength is not especially high.
Broadsword and shortsword, or broadsword and poniard: More effective against large numbers of individually easy-to-kill unarmoured opponents. Also, you could pass for an ordinary man-at-arms-about-town, rather than looking like a maniac with a huge axe. Great for pirates and thieves, since sneak attack damage will benefit from hitting with additional attacks.
Broadsword and axe: As for broadsword and shortsword, but you can throw the axe if you need to.
Bill: Greater versatility, can make trip attacks, set against a charge.
Paired Zhaibar knives: More raw damage than any other weapon combination.
Broadsword and large shield: Enemies miss you 20% more often.