Natural Attacks
Heya, I designed a power just for that purpose. I'm going to put it below and it will at least give you something to work with.
Natural Weapons
Base Rank: 4
Effect: You are gifted with some manner of natural weapons, claws, extraordinarily hard fists, fangs, a tail, grafted blades etc. All attacks with your natural weapon no longer provoke an attack of opportunity and you cannot be disarmed. These weapons do 1d4, x2 damage.
Enhancements:
Vicious Attacks
Ranks: 2
Extra Effect: You up the damage you do with your natural weapons by one die, for example, from 1d4 to 1d6.
Multiple? : Yes, every extra 2 ranks ups the damage by another die, 1d6 to 1d8 and so on to a maximum of 1d12.
Keen Attacks
Ranks: 2
Extra Effect: Your natural attacks now threaten on a natural roll of 19 and 20
Multiple? : No
Bloody Attacks
Ranks: 4
Extra Effect: Your Critical Modifier goes up by one, from x2 to x3.
Multiple? : No