The dragon dagger has a special attack called Puncture. It uses 25% adrenaline to deal two quick attacks that deal increased damage with an increased accuracy. The off-hand dragon dagger does not have this special attack.
It is important to note that the dragon dagger special hits higher and with higher accuracy depending on the off-hand weapon that you are using, down to a minimum of tier 60 weapons so the player is not penalised for using a bronze defender, for example.
Prior to the Evolution of Combat, the dragon dagger was held with a reverse grip with the blade pointing down.
Players with poisoned variants of the dragon dagger in their bank had them replaced with notes of the unpoisoned dagger following the Evolution of Combat update. It is one of the few known cases where noted items could be found in the bank.