In the GURPS Alien Menace game, we use armor as dice. So their DR 35 combat armor is now 10d on the torso. The 3d (5) blasters knock that down to 2d armor, doing 1d burn injury per hit through the torso.
It’s fast and easy.
But we wanted to come up with a rule for grazes, and have settled on:
If a defense is missed by 1, a hit turns into a graze. Armor DR is doubled, and if any penetration occurs, injury is only one point of damage per 6d of injury, minimum one point of injury.
This makes it possible to get hit by a .50 BMG for less than 12 points of damage, which is something I tried to deal with (badly) in Armor Revisited (Pyramid #3/34: Alternate GURPS), and TBone did much better in his article in the same issue: Ten Tweaks.
I wanted to keep the quick and easy feel of Armor as Dice, not change any rules. So if you biff your defense by 1, you get grazed. Seems like it would be fair to allow one to spend a destiny point for this as well, or maybe even a two-fer. One point can turn that attack from success into failure anyway, so you can spend a point and turn two or three hits into grazes . . . maybe even on different shots. It’s terribly meta, but “get missed once, or grazed two or three times” seems not awful.