Just a stray thought I had while taking a few moments to go over some NPC stats:
One criticism of Feints in GURPS is that they can be very swingy. That is, since it's a Quick Contest of Skills, an especially good roll by a good fighter versus a bad roll from a poor fighter can mean a massive penalty. Conversely that good fighter can roll mediocre or poorly versus a good roll and end up inflicting a small or non-existent penalty.
In other words, sometimes in high-powered play it's "He defends at -20!" and sometimes it's "He defends at -1." Sometimes it's no effect at all. Usually it's neither, and you just get a reasonable penalty that reflects the relative skill levels of the fighter.
Mostly that doesn't bother me. It's generally kind of fun.
Mostly what bothers me is that it's yet another number to track for a GM when a PC feints a foe in the middle of a large fight. Or interweaves Feints with multiple attacks with different levels of Deceptive Attack and native technique defense penalties onto them. It can get hard to keep it all straight.
Here is an alternative way to run Feint. It is, as yet, untested in play. But at first look it seems like it could be a reasonable way of changing how Feint works to address both the "swingy" nature and the tracking of a variable penalty.
Feint - Roll a Quick Contest of Skill vs. your opponent like a normal feint, using all of the modifiers and rules appropriate to that feint. If you win the contest, your opponent suffers twice the usual defensive penalties inflicted by your technique, Dual-Weapon Attack, Deceptive Attack, and so on. If you tie or lose the contest, the feints fails and has no effect.
Example 1: Vryce attacks a lizard man chieftan while Great Hasted, and chooses to All-Out Attack (Feint) on his first turn, naturally following it up his Trademark Move. He rolls his Two-Handed Sword-27 versus the chief's Broadsword-20; Vryce rolls a 15 and makes it by 12, the chief rolls a 10 and makes it by 10 - Vryce wins. His Trademark Move is a Rapid Strike and a Deceptive Attack -4 (-8 to hit). He makes both attack rolls. The chief must defend against each of those strikes at -8, not -4, because he was successfully feinted.
Example 2: Harmonious Sun Fist, aka Sunshine, uses a Feint against a rival for the rank Master of the North Wind. He makes his Feint roll by 6, his foe by only 1. He wins the contest. On his next turn, he swings his nunchaku at his rival, making it a Deceptive Attack -1, and hits. Nunchaku give a -2 to Parry, -1 to Block, and Deceptive Attack is a -1 to all defenses. His rival parries at -6, would block at -4, and dodges at -2! Not surprisingly, he chooses to attempt to Dodge.
Hopefully the examples make the application clear.
Pros: Roll is success or failure. Your effectiveness feinting is based on your ability to follow up. You don't need to calculate the win or loss on a contest or even conceal that one occurred. Vastly less swingy if you dislike those sorts of things. Very predictable for the feint-er. Frighteningly useful for people with flails and who use AOA (Jump Kick) or Counterattack a lot.
Cons: Means Feint is only useful for higher skill attackers, not just those with high relative skill, because high skill is needed to absorb the penalties for DA, DWA, and so on. Cases like Spin Kick and Spinning Strike aren't addressed, however, and would need to be resolved with the normal rules. Makes it really obvious why Telegraphic Attack won't work after a Feint, because giving +2 to defend is useless when you double defense penalties.
Alternative: Instead of doubling penalties for Deceptive Attack, you can say it allows Deceptive Attack at a -1 for every -1, or doubles the defense penalties from an attack. This can get tricky, though, as Trademark Moves that involve Deceptive Attack suddenly have a higher skill or double the penalty anyway, and it can lead to longer fights as players try to hair-split additional levels of Deceptive Attack versus a -1 to skill. (This was my original idea, and I rejected it because of those downsides.)
As a second alternative, you can apply a minimum penalty of -1 for being Feinted, essentially giving a -1 or twice the defense penalties, whichever is worse for the defender.
Like I said, I haven't tried this. I think it's elegant and interesting. It's certainly a change, and I'd bet that my players would reject it because it raises the minimum value but caps the maximum value. That Two-Handed Sword-27 isn't a typo or an aspirational skill level in my DF game. Trading off the high chance of, say, winning by 12+ against the vast majority of foes vs. the certainty of a -8 to defend from your Deceptive Attack might not seem like a good idea. Especially when you need to fight with a stack of penalties that restricts your attack, but not Feints - such as foes with tiny hit locations that must be hit.
(Also see Douglas Cole's discussion of this: Alternate Feints vs. Setup Attacks)