This one is fairly self explanatory. Ingredients*: one old t-shirt, one snap fastener
It makes a great superhero cape and requires the minimum of sewing ability. I was tempted to just leave the neck of the t-shirt whole but then I though "strangulation hazard", so I added a snap fastener. I didn't even bother sewing up the edges, t-shirt fabric pretty much doesn't fray. Five minutes work!
* I did a latin course with the Open University a couple of years ago. There were a few delightful moments of recognition, like the time I realised that "ingredior" is the verb meaning "I go in" -- hence "ingredients" == "things that go in".