Impish Bite (4e Feat)
From D&D Wiki
Impish Bite [Racial]
Benefit: Your bite is a light blade weapon with which you are proficient. It causes 1d6 damage, has a +3 proficiency bonus, and has the off-hand property. You can enchant and disenchant your bite, and it does not turn into dust when disenchanted.
Special: You can make basic melee attacks with your bite if you have polymorphed into a giant rat or giant spider with the impish polymorph racial utility power.