A great scimitar is too large to use in one hand without special training (the appropriate Exotic Weapon Proficiency feat). You can use a great scimitar two-handed as a martial weapon. Great scimitars are most often the personal weapons of heroes, crafted as masterwork weapons and inscribed with the hero's deeds and the weapon's name on the blade. Such names commemorate a great event in the hero's life, such as "The Blade of the Hundred-Day Sandstorm."