The best part about this instructable is it made from ALUMINUM CANS!! This is because recycling is very important to me, and also, there are few things as cheap as aluminum cans.
Step 1: Needful Things
Soda cans (14 should do, but you may need more if you have a short coat and need longer arms)
Trench coat, or any coat that goes down to your knees
Googles or sunglasses
Spiderman Action figure (Optional, but I think you want to use one anyway. You can probably find a cheap used one at a flee market, or Comic convention)
Silver metallic spray paint
Tin Snips or a pair of kitchen shears you don't mind trashing
A square Ruler (an adjustable one is helpful, but not necessary)
A punching tool (I used an Awl, but a nail and hammer'll work just fine)
Hot Glue Gun
Step 2: Prepping Your Cans
Start by using your square ruler to make a mark 2 1/4 inches above the bottom of the can. Continue this all around your can until you have a dotted line, then draw a solid line over it.
Now carefully cut along the line with your pen knife. While doing this, I accidentally deviated from the line a few times. If you make the same mistake, you can trim the bumps with you tin snips.
Finally, take your awl (or nail) and punch a hole through the center of can halves.
Step 3: Making Claws
Now use you pen knife to cut the top off. Next, take your tin snips and cut out claw fingers so they taper outward. Then, fold the flaps of the can that are not fingers into the can where no one will see them. Finally, put a bend in the middle of the fingers, making a knuckle, and then fold the fingers outward at the bases. Try not to bend the aluminum back and forth too much, or it'll snap.
Step 4: Painting
You can also draw a black line at the base of each claw to make look more like a joint than a solid piece of aluminum.
Step 5: Putting Them Together!
Now here is where it gets interesting. Tie a slipknot about where you think the next segment/can will rest, but make sure the lower part of the string is the adjustable end. This way you can adjust the distance between the knot and top of the claw if you need to once you slide on your next can. Remember, the knots will need to be a little higher for arm segments made from the top of the can.
Once you're satisfied with the placement of your knot, lock it in place with hot glue. Continue these steps until you've reached a desired length; I chose 6 segments including the claw.
Now that you have an arm that meets your personal standards, determine how low you want your arms to dangle, then make a loop at waste level, and slide it onto your belt.
Step 6: Final Touch
Your technically done. If you opted to purchase the Spiderman action figure, insert it into one of you claws, and hot glue them shut onto it. Hopefully this will communicate your costume to everyone whom only saw the movie.
Also, if your arms are jiggling more than you'd like, you may run a strip of clear scotch tape down one side. This will slightly restrict it's movement, and prevent you from sounding like a junkyard wind-chime.