You'll need large pieces of thick, sturdy cardboard, craft glue, paint, ribbon, and optionally a flat corner bracket which you can purchase from your local hardware store. Draw the shape of the axe you want, blade and handle, onto a piece of paper. The simpler the shape, the better it will work. Trace this shape onto at least four pieces of cardboard (six is better) and cut them out with a box cutter knife. If you're a kid, get help from an adult with this. It's very easy to stab yourself or cut your finger off! Take one piece of cardboard to act as the center. Glue the corner bracket at the L between the handle and the the blade. You can also place a thin stick or dowel rod in the handle piece if you want to. Glue all of the layers together, with the reinforced section in the middle. You can use the box cutter to bevel the edges of the blade section if you want. Once this is done you can cover the whole thing in duct tape, paint it to look real, or wrap the ribbon around the handle to give it a really authentic look. Enjoy your new battle ax!

Summary:
Gather your materials. Make your template. Cut out your pieces. Reinforce the center. Glue the pieces together. Add finishing touches. Done!