Writing games are tricks, exercises, things to try to get your writing brain in the mood. I find them useful when a story's giving me trouble - I can't think of a way out of the corner, or I can't think of a corner to get into, or I'm just not feeling in the right mood to write that story - as well as generating new ideas, and just keeping my writing-mind in shape. And on the plus side, they're usually fun to try, and you can end up with the germs of some great little stories.

Roll to disbelieve

Pick something you believe - the more strongly you believe it, the better. It needs to be something that's a matter of faith, or morality - something with an argument for the other side. The theory of gravity, for example, won't help you much here.

Now create a character who believes the opposite of what you do, and write a short monologue expanding on his belief. It'll help if you give him a plausible scenario to be having this monologue in the first place. (I'm using the male pronoun for ease, it could easily be a female or a chair, if you'd like). You must not allow him to be a characterture of his belief, or instantily villified - keep him a rounded, believable, sympathetic character in his own right.

The point of the exercise is to step outside your own belief patterns for the purposes of creating story. It's a difficult thing to master - a lot of our beliefs are so deeply ingrained that they're difficult to even detect even with a great deal of introspection. But to create characters, especially villains, that have depth and believability, you need to be able to stretch outside your own mental structures.