It's like a top hat but shorter.
It's Hat Guy's hat from the web comic XKCD
Step 1: Materials
Step 2: 2 Circles
First of all you have to cut a circle. The size that the top of the hat should be.
Then cut another circle that is a few inches bigger than the first.
Step 3: Head Hole
In the bigger circle you should cut a head hole. Not enough to go over your head but just rest on top of it.
Step 4: The Connection.
Create a small strip of cardboard that is the length of the circumference of the small circle. and the tallness that you want the hat to be.
Use duct tape to connect it all together.