I love cosmetic purses, I have a whole drawer of them and one each for my handbags. They are easy to sew and would make the ideal Christmas gift.
Make them any size you wish, add a boxed bottom or curve the corners. Options are endless, so are the uses for them.
They don't need a lot of fabric so they're great for using up scrap fabric. I like to add laminated iron on vinyl to mine so they are easy to wipe down.
Here is a tutorial I did a little while back, showing you how easy they are to make.