You can make anything out of cardboard with a bit of experimentation and practice. For this project I taught myself how to create a scale replica of an object. All I used was a box cutter, hot glue, and lots of large sheets of cardboard.
I went to Sam's Club for most of the cardboard; they have large, flat, clean sheets between their pallets that they let you take for free. They I found that Sam's Club pallets also have different qualities of cardboard so you can use cheaper, more flexible sheets for curves and firmer cardboard for clean cuts and large sides.
Its important to keep your blade new and sharp to keep the edges crisp and clean.
One technique I used to get nice curves was rolling the cardboard with the grain of the corrugation. Keep that in mind when laying out your cuts if you plan on having smooth curves.
In the photos you can see the sketches and measurements I made before I started cutting. I actually measured all the main points of a hammer I had and then scaled it up so all the proportions would be accurate and look right. A little planning really helped things go more smoothly as I worked on it, I still had to make some adaptions as I worked on it though. So be flexible!
I love the fact that I made it tall enough to stand under, it really makes it feel surreal! It also barely weighs anything!
Get out there and start having fun with cardboard! Its cheap, lightweight, and easy to play with. I hope I inspired some creativity!