Modifiers

Enhancements

Strikers
Special Enhancements
Swing Damage: The Strikers' damage is based on Swing instead of Thrust. +50%

Claws
Special Enhancements
Swing Damage: Applied to Talons or Long Talons, allows them to do Swing/Cutting or Thrust/Impaling damage. +50%

Limitations

Psi Modifiers
Special Limitations
Leaves Signature: This is essentially a Nuisance Effect, worth -5% if the signature is only detectable with specialized equipment or through the use of Psi powers, or -10% if it is detectable by a normal person without the aid of special equipment (i.e. leaves a glowing hand print on the victim). If the signature lasts an unusually long period of time (over 24 hours) it's worth an additional -5%

Power Varies with Hit Points/Fatigue Points
Special Limitations
For Advantages this is essentially an Accessibility Limitation: Only while above X HP. Appropriate cost would be:
Only while above 1/2 HP: -30%
Only while above 0 HP: -20%
Only while above -1xHP: -10%
Only while above -2xHP: -5%
Loses 1/4 of it's levels per HP "Threshold", -20%
Loses 1/3 of it's levels per HP "Threshold", -25%
Loses 1/2 of it's levels per HP "Threshold", -30%

For advantages that lose effectiveness if you lose Fatigue points the appropriate with the thresholds for the Accessibility are:
Only while above 3/4 FP, -30%
Only while above 1/2 FP, -20%
Only while above 1/4 FP. -10%
Loses 1/4 of it's levels per FP "Threshold", -15% (at 0 FP the advantage stops functioning).
Loses 1/3 of it's levels per FP "Threshold", -20%
Loses 1/2 of it's levels per FP "Threshold", -25%

For Disadvantages, this is essentially a Mitigator (though mitigators are usually items or substances, I see no reason not to expand it to conditions):
Only while below 1/2 HP: -40%
Only while below 0 HP: -60%
Only while below -1xHP: -80%
Gains 1/4 of it's levels per HP "Threshold", -50%
Gains 1/3 of it's levels per HP "Threshold", -45%
Gains 1/2 of it's levels per HP "Threshold", -40%