"Which non-D&D supplemental product should everyone know about? Give details."
Now here's a game I can talk about, and that I want to talk about, and holy shit people Lovecraft loved cats so much his name has love in it and someone decided to do something about it and I'm totally not talking about the GenCon Kickstarter I totally backed and THIS IS THE INTERNET PEOPLE SO GET EXCITED ABOUT CATS!
Ha, I bet it would get really annoying if I kept writing in that voice for the rest of this post.
In all seriousness, when I'm talking Cathulhu, I'm referring to the Worlds of Cthulhu #4, which introduced CharGen rules for creating feline investigators. The mechanics of doing so are super-involved, and focus on what breed you are, as well as what adorable tricks you may have up your sleeve.
And Wash is a skill. I've homebrewed a rule, thanks to my buddy Scott, that if a catvestigator (heh) fails his roll to wash, he loses Sanity, now called Sentience.
Heh. Catvestigator, get it? Well, when one loses Sentience, they start experiencing adorable cat problems, like toilet troubles, upset tummies, or spontaneous spraying. If they lose all their sentience, cats go feral.
Seriously, though. Find a copy of Worlds of Cthulhu #4 and run this. It's totally worth every bit of adorability your players will create in-game.