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).

Pros

Good range

Comfortable fore-grip

Accurate scope

Mag as handle (for more power)

Ten shot

True trigger

Sturdy, comfortable stock

Bolt action

Can be modified to shoot exploding rockets!

Cons

Ugly mag pusher

Uncomfortable handle/mag

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).