Wraithstrike

By presenting your weapon with an overly dramatic flourish and calling out with a sickly-sounding moan, you complete the spell. As you do so, your weapon becomes translucent almost to the point that you cannot see it, though it still weighs as heavily in your hand.

(Spell Compendium, p. 243)

Originally posted on D&D tools

Transmutation
Level: Sorcerer, Wizard 2, Assassin 3,
Components: V, S,
Casting Time: 1 swift action
Range: Personal
Target: You
Duration: 1 round

While this spell is in effect, your melee attacks are resolved as melee touch attacks rather than normal melee attacks.