The Ravager is the most powerful K'nex gun I've made. It has a range of almost 70 feet (with the right bands) and has a pretty quick rate of fire for a non automatic gun (meaning you have to pull something back each time you want to fire).
Mag as handle (for more power)
Sturdy, comfortable stock
Can be modified to shoot exploding rockets!
Ugly mag pusher
Non removable handle/mag
Uses three broken pieces
I hope this gun has given you some inspiration for some of the mechanisms for your guns. I have made instructions but I've very little experience so they're not that good however they should be adequate to make the gun.
Step 1: The Scope
Step 2: The Body
All broken pieces are seen in the 3rd picture. There are two white rods with the ends cut off (in the picture they are grey) and the end of any rod longer than a white one. (It' also grey).