SRD:Collision

Collision: Collision weapons psionically increase their own mass at the end point of each swing or shot. Such weapons deal an extra 5 points of damage on each successful strike, in addition to the weapon’s enhancement bonus. Bows, crossbows, and slings bestow the extra damage upon their ammunition.

Moderate metacreativity; ML 10th; Craft Psionic Arms and Armor, matter manipulation; Price +2 bonus.