In this post Tim of Gothridge Manor talks about the official guard figure. In it he mentioned the Knight Killer Crossbow. This weapon originated out of a GURPS campaign where everybody played a member of the poor suffering town watch. Among the tactics the players developed was a super heavy that could only fire once as you needed to winch it up to recock it this took at least 6 rounds.
The SoP (standard operating procedure) was for everybody to fire their knight killer, drop it, and then ready their normal weapons. Not everbody hit but those who did tore into their opponents. Being GURPS this often meant an opposing adventurer was taken out in one shot. Those who survived were often grievously wounded.
When I wrote up the Majestic Wilderlands I included it as part of my price list. It was folded into the general boost that crossbows got. All crossbow got a bonus to hit because of superior accuracy. The Knight Killer Crossbow is patterned after the european arbalest.
Crossbow, light: 30d*. 6.0/lbs
Acc:+2 RoF 1 Rng:60 ft Dmg: 1d4+1 (Bolts)
Crossbow, heavy 38d, 6.0/lbs
Acc:+4 RoF 1/2 Rng:80ft Dmg:1d6+1 (Bolts)
Cross., Knight Killer 46d, 6.0/lbs
Acc:+4, RoF 1/6, Rng:100ft Dmg:1d20+2 (Bolts)
Prodd 38d/ea 6.0/lbs
Acc: +2, RoF 1, Rng: 60ft, Dmg 1d4+1 (Bullets)
*d = denarius = silver penny = silver piece.