Weapon Parries against Unarmed Attacks do Half Damage

 This is a house rule in my games. I believe I got the idea from Dungeon Fantastic. 

 Basically, the default in GURPS (and DFRPG) is that a successful armed parry against an unarmed attack allows the defender to wound the attacking limb with their parrying weapon. This is an immediate free action (normally at full skill) by the defender on the attacker's turn, and doesn't otherwise impact the defender's actions on their next actual turn at all. The free damaging parry also can't be prevented by the original attacker; it might miss of course, but at DF-level PC competence that is unlikely. 

 By RAW this free counter attack does the weapon's normal damage for that wielder. This is quite powerful, especially against tooth and claw monsters whose primary defence is a good dodge. It can end up being the main way that the PCs can hit such critters. My house rule doesn't reduce the PCs' chances, it just halves the resulting damage (rounding down). This accounts for the fact that while the weapon parry could cause hurt, it isn't as powerful as a full strength attack. That is still bad for wild animals, but it feels fairer and less egregious somehow.