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.

 Protip: Moths plus bugspray does not lead to dead, quiet moth that lets you sleep. It leads to hyperactive, totally-librarian-poo moth going like a motormower in various corners of your room for hours zipping so fast that no number of shoe-whacks will catch it. And I do mean hours. This is not good if you do not like moths. 

Clowns are scary

Simple concept - what's something you're afraid of? Heights? Public speaking? Small, harmless furry winged insects? This works best if you pick something that isn't typically scary, something that you'd generally not want to admit to being frightened of, because people look at your sideways and say "Really? Moths? It's an insect, and it doesn't even have fangs. What's so scary about a moth?" Find what it is about them/it that frightens or unnerves you. Have at think for a moment.

The aim of this exercise is not to write an essay titled "Why I hate moths and any sensible person should too", but to make the reader really feel what's so creepy/terrifying about it. Come up with a scene, a snippet, an image that conveys what it is that bugs you so much (pun unintended) about your chosen 'thing', make the reader's skin crawl, or their spine shiver as yours does when confronted with your personal moth.