You may already be asking, “Why on earth would these guys write about a crystal ball?” Let me say right off the bat that I'm not interested in this thing as a centerpiece or because I want to cast spells or whatever. The reason it's cool is that you can use it as a spherical lens for taking fun inverted-effect photos.

In doing a mini-review of the similarly designed (but way more expensive) Lensball, Steve Huff shows what a crystal ball can do for your photography:

Since the sphere is made from K9 crystal, it's both durable and offers high visual clarity throughout. When you're not using it for photos, it can make a nice bit of decor by using its included stand — that is, provided you keep it out of constant, direct sunlight to prevent its magnifying effect from starting a fire. It could also work well as a prop for theater actors and street performers. Or, give it as a novelty gift to a photographer friend. Get creative!

Whatever your use-case, you can get this crystal ball for $15 on Amazon.