GURPSよろず

Claws
see p. B42
Many martial artists toughen their hands by punching a heavy bag, wooden post, etc. The usual goal is to condition the hands so that hitting hard surfaces is less risky (treat this as DR; see Damage Resistance, p. 43), but some unorthodox exercises are intended to harden the hands into deadly weapons. These include striking iron or steel, driving extended fingers into hot sand, and applying rank-smelling unguents. The results often have a colorful name, such as “iron hand” or “eagle claw.” Represent this using Blunt Claws [3] – and perhaps other traits.
Realistically, any toughening extensive enough to improve punching damage would irreversibly damage the hand. The GM should only let realistic fighters buy Blunt Claws if they also take Bad Grip 1 [-5]. The package is a net disadvantage (-2 points). Since Bad Grip 1 gives -2 to grapple or use melee weapons, this severely curtails the martial artist’s other combat options.
In a cinematic campaign, the GM may relax this restriction and allow esoteric, non-destructive exercises or amazing ointments. If so, individuals with Trained by a Master should have access to such methods and be able to buy Blunt Claws without Bad Grip. If those without Trained by a Master want this advantage, they can either get it the hard way (with Bad Grip) or pay 10 points for Unusual Background (Access to secret hand-toughening exercises).
It’s possible to modify just one hand. This doesn’t reduce the point cost of Claws or Unusual Background, but Bad Grip must have the -80% limitation “One hand only.” This reduces its value to -1 point and means that its -2 penalty applies to one-handed tasks with the modified hand. For two-handed tasks, the penalty is only -1.
Those who wish to do this in play should see Learnable Advantages (p. B294). Base the time required on the cost of Blunt Claws (3 points). Where applicable, any Unusual Background must be bought before training begins, while Bad Grip appears at the end of this time.
For another option, see the Limb limitation under Striker (p. 47).