Razorfangs

(Spell Compendium, page 168, DnD 3.5)

Transmutation

Level: ; Sorcerer/Wizard 2
Components: V
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: 1 round/level

You speak the words of this spell and your claws shine with lustrous yellow radiance, growing more slender and sharper as you watch.

Choose one of your natural weapons that deals slashing or piercing damage (such as a bite or a single claw). That natural weapon's threat range doubles (in most cases, becoming 19—20). The effect of this spell does not stack with any other effects that increase a weapon's threat range.