So my son wanted a Minecraft sword to run around the house with. I've managed to stay well away from Minecraft, but decided to make him one out of cardboard instead of dropping a large amount of cash on a foam one. It was pretty easy to find a large picture of a sword on Google, and then print it out on a couple of sheets of A4 paper. These were then glued to some scrap cardboard from a box using spray mount.
After allowing to dry this was then cut out using a steel rule and a scalpel. As it's a little thin a second one was made, and then these glued back to back with the edges coloured using felt pen. Finally cellotape was wrapped around it to help protect it against all the bumps it will get while it's swung around, and to stop the two halves coming apart.
If I had to make one again I'd change it a little. Firstly I'd make it bigger - this one works well as my son's hands are quite small, but the squares are smaller than one his official "Steve" head. I'd also cut out the card first and seal the edges before adding the printed paper, so it has smooth edges.