I saw this post this morning, and I was inspired. Better bow critical failures for GURPS can be done! It can be worse than "weapon breaks" or "you drop your weapon."
Let's see how those could work in GURPS terms:
2-3 would just be "broken weapon." Optionally, the grip hand injury would be a HT roll - failure means a crippling injury. Roll vs. HT daily to recover.
4 would just inflict 1/2 bow damage on the hand, DR protects normally.
5 means the arrow is stuck, like a pick (Picks, p. B405). The bow is useless until the arrow is freed.
6 Hahahahahah. Sorry. Temporarily has One Eye for 1d seconds; after that roll HT every second to recover.
7-8 string broken.
9 string broken, but the arrow goes off somewhere; it's a critical miss, so you absolutely do not hit your intended target, but roll for friendlies along the path! Unfair because it has no chance to hit people you don't mind hitting? Well, next time don't roll an 18. We've already determined something bad happened, this is a roll to determine what it was. If it suddenly becomes "nevermind, you still kill some bad guy" it's not a critical failure, really.
10-11 rip open your arm armor; it only protects on a 1-3 on 1d, or subtract 3 from the odds of protection if that applies.
12 is as 10-11, but also take 2 HP of injury from a snapping bow string and roll vs. Will (High Pain Threshold and Low Pain Threshold apply) to avoid dropping the bow!
Fun stuff. I may need to see how to fit these into a proper table for GURPS . . .