This is not a balance issure, this is a list of quirky effects that one could apply to a weapon. It is not intended to be balanced, but interesting.
Flaming: Player gets Energy Resist Fire 5.
Frost: Player gets Energy Resist Cold 5.
Corrosive: +1 to damage on metal foes, and +1 to CMB and damage when sundering a metal object.
Shock: +1 to hit against foes wearing metal armor. Another stackable +1 if the foe is wet. Add another +1 if the fluid is especially conductive, like seawater.
Agile: Since the weapon itself seems to be unusually nimble, the holder gets +1 to CMD against that weapon. Disarm, Sunder, etc.
Keen: Extra-sharp? Player can use the weapon as a surgical instrument, emergency boning knife, shaving razor, mandolin, etc...
Other ideas?