GURPSよろず

Grab and Smash!
Grapples can set up vicious strikes. These tactics are realistic but complex. It’s the GM’s call whether to allow them.

All-Out Grapple and Strike
Martial artists and brawlers often grab opponents and pull them into thrusting attacks. Such strikes are powerful and hard to avoid. Examples include yanking a head into a Knee Strike (famous in Bando and Muay Thai), throwing an Uppercut in a clinch (illegal but common in Boxing), and pulling someone onto a knife. The perks Clinch (p. 51) and Neck Control (p. 50) are handy here!
This is an All-Out Attack (Double). Use the first attack to grapple your rival. If it works, he’ll suffer the standard defense penalties against the ensuing strike; see Defense While Grappling (pp. 121-122).
Your second attack can be a strike with anything except the arm(s) used to grapple. This is a close-combat attack. If you use a weapon longer than reach C, see Long Weapons in Close Combat (p. 117).
If the grapple works and you hit the grappled location with a thrusting attack, your strike gets the damage bonus for All-Out Attack (Strong). This also applies to blows to the groin, spine, or vitals if grappling the torso; the eye, jaw, or nose if grappling the head; or an artery or joint if grappling a location containing such a target. You may retain your grapple after striking or relinquish it immediately.
Use these rules only on the turn when you initiate your grapple. You must All-Out Attack to grapple and receive bonus damage. To brutalize an adversary you grappled on an earlier turn, use All-Out Attack (Strong).

Kiss the Wall (Carpet, Car Door, . . .)
If you’ve used two hands to grapple a foe and you’re standing or kneeling, you can ram him into a wall or other massive object within a yard – or the ground, if he’s lying down. This isn’t a Judo Throw (p. 75), but an attempt to hold onto your victim and propel him using your own momentum.
This is an attack rolled against DX, Brawling, Sumo Wrestling, or Wrestling. You can target any hit location but the feet, at full penalties. If your victim is lying down, you can only target his face or skull. Your opponent may either dodge or parry with a free hand, subject to Defense While Grappling (pp. 121-122).
A successful attack inflicts thrust crushing damage, +1 for a hard surface, plus your skill bonus. Treat the ST bonus for Sumo Wrestling or Wrestling as a damage bonus. A critical miss means you slip, take this damage to your face, and lose your grapple!

Twofers
You can knock two foes together! Use the rules above, with these changes:

All-Out Grapple and Strike: As your initial grapple, make a Dual-Weapon Attack (-4) against adjacent foes in close combat. Both defend normally. If you grapple only one, your grapple counts but you can’t strike. If you grapple both, make a DX, Brawling, Sumo Wrestling, or Wrestling roll to ram them together. They may defend as usual. If both fail, you inflict thrust-1 crushing damage to the grappled location on each. The only damage bonus is +1 if you grapple two skulls and knock them together.
Kiss the Wall: You may ram your grappled adversary into any hit location on an enemy within a yard. Use the worst hit location penalty; e.g., bashing a face (-5) into a leg (-2) gives -5. Your second opponent defends normally, although the incoming body counts as a weapon with weight equal to the first victim’s ST (p. B376). If either foe defends, nobody is hurt. If both fail, each takes thrust crushing damage, plus skill bonuses. The +1 for a hard surface applies only when ramming skulls together.