Prismatic Burst (3.5e Equipment)
From D&D Wiki
Prismatic burst: A prismatic burst weapon functions as a prismatic weapon that also explodes with multicolored energy upon striking a successful critical hit. The energy does not harm the wielder. In addition to the extra damage from the prismatic ability, a prismatic burst weapon deals an extra 1d4 points of acid, cold, electricity, fire and sonic damage on a successful critical hit. If the weapon’s critical multiplier is ×3, add an extra 2d4 points of each damage type instead, and if the multiplier is ×4, add an extra 3d4 points of each damage type. Bows, crossbows, and slings so crafted bestow the energy upon their ammunition.
Even if the prismatic ability is not active, the weapon still deals its extra damage types on a successful critical hit.