Daikatanas are a warrior only class of weapon in Cabal. They are similar to the Greatsword, but the stats are reversed. The Daikatana favours speed over power, unlike the Greatsword. This gives it a slightly faster attack rate, but at the cost of lower base attack power and a higher agility requirement.
Thus, they are less popular than the greatsword, due to most warriors preferring higher base attack power.