Well, over the night (10.00 PM to around 1 AM) and some during midday (around 12.00), I made a Knex Minigun (although it is not mini at all, but very large). In case you do not know, a minigun is a large machine gun, having nothing to do with the word "mini".
It uses a lot of pieces and is very cool. There are two handles sticking out from the side and the gun is sturdy enough to hold up to 40 clips on a chain.
Unlike past knex machine guns, the gun does not have its chain in a loop, but it is just fed through by a motor and falls off in the end.
I am working on a tripod/base for it to sit on, but so far all of them have broken down under its weight.
Please post on this slideshow if you want me to post instructions or not.
Holds up to 40 rounds.
Is actually pretty light.
Does not use too many exotic pieces.
Fairly simple to build.
The tripod (coming soon) allows the gun to turn 360 degrees and point up and down.
If the gun is not on the tripod, the handles will not support its weight when the chain is on, so there is a grip underneath.