А давайте обратимся к тому, что нам говорит новый официальный FAQ по GURPS с сайта SJGames.com
What are the rules for fighting with two weapons?A character who attacks with two weapons is at -4 on both attacks when doing so, unless he has Extra Attack. He has an additional -4 on the attack made with the weapon in his off hand (for a total of -8 and -4, or -4 and 0 with Extra Attack). To buy off the -4 for attacking with two weapons, use the Dual Weapon Attack technique; to buy off the -4 for using the off hand, use the Off-Hand Weapon Training maneuver (or buy the Ambidexterity advantage).
When aiming at multiple targets, against which do I get the aiming bonus?Against the first target.
If I have an Extra Attack, do I really have to use my second hand to do it? Feel free to let normal people have one Extra Attack with their primary weapon arm. That lets Weapon Master types make three attacks (two as a Rapid Strike, plus a third at full skill). GURPS Powers will have a few thoughts on allowing even more attacks with the same limb.
Can I use Dual-Weapon-Attack with two different weapons? If yes, how does it work? Yes, it is possible.
When making a Dual-Weapon Attack, roll against your DWA technique with each weapon. If you haven't improved the DWA technique for one of your weapons, you roll at -4 with that weapon. For instance:
Left hand wields a broadsword & right hand wields a broadsword: Left-hand attack rolls vs. DWA (Broadsword) to hit, right-hand attack rolls vs. DWA (Broadsword) to hit.
Left hand wields a broadsword & right hand wields an axe: Left-hand attack rolls vs. DWA (Broadsword) to hit, right-hand attack rolls vs. DWA (Axe/Mace) to hit.
Left hand wields an axe & right hand wields a broadsword: Left-hand attack rolls vs. DWA (Axe/Mace) to hit, right-hand attack rolls vs. DWA (Broadsword) to hit.
Left hand wields an axe & right hand wields an axe: Left-hand attack rolls vs. DWA (Axe/Mace) to hit, right-hand attack rolls vs. DWA (Axe/Mace) to hit.
In all cases:
Lacking a needed DWA technique means striking at weapon skill-4.
The off-hand attack is at an extra -4, unless the wielder has Off-Hand Weapon Training with the weapon in the off hand.
Thus, a fighter who customarily fights with a broadsword in the master hand and an axe in the off hand would probably have DWA (Broadsword), DWA (Axe/Mace), *and* either Ambidexterity or OHWT (Axe/Mace).