Here is my idea for the competiton.
First of all, i found this a lot of fun to create, mainly because i love the whole 'home-made gun' thing. I was much a fan of it in fallout 3 and love the fact it is somewhat similar to the weapons in Metro 2033.
Below is my entry, but the things that make up this weapon which i have named 'The Mum Nailer' (yes, i am aware it is sexually suggestive, but it was not my intention) are as follows:
1 x bag of Steel nails = Ammo
1 x Spray can = Ammo Cannister
1 x Metal Tube = Rifle Barrel
1 x Binocular Lens = Scope/Aiming Sights
1 x Kitchen stove/oven ligher = Trigger
1 x Breadknife/Kitchen knife = Gun handle
1 x Roll of Duct-tape = Holding the cannisters Together along with the gun
1/2 x Pneumatic Cannister (optional additional cannister can be mounted on other side) = Projectile Firing
If you're out of nails, just load up some of your dogs biscuits into the gun and fire away, that is, if your dog has not ended up with rabies or mutated like some of the things in metro 2033...
The range would be fairly good, but for best effect you'd want to be somewhat close to the target, which is a bit risky but i am sure you can manage a stealthy approach with a small semi-handgun type weapon.
About the name, well, i thought about mostly kitchen appliances when first creating this, thus the kitchen oven/stove lighter, kitchen knife, General kitchen things mothers have in their arsenal of utensils.
Just threw 'nailer' on the end, due to the fact it shoots... well.. nails.
So there it is, took me a while trying to figure photo shop out. Enjoy!
Link, incase picture did not work, http://i610.photobucket.com/albums/tt181/Genephyx/Mumnailfinal.jpg