I've heard it will kill mold, mildew and ringworm, but I've always thought I'd rather stick to plain ole' bleach and athlete's foot cream. (FYI: if you take in foster kittens or ever plan to do so, just go ahead and keep athlete's foot cream for ringworm on hand. It's a buck at the Dollar Tree and you WILL need it eventually. We've had 7, count'em 7, kittens turn up that we had no recourse but to raise up since we moved here. So, yeah, there's a tube in the storage room that turns into our kitten HQ. . .) I've also heard of people who use it to kill fleas, but I've only HEARD of that. It seems to always come up in conversations about what you can do with Listerine, but I don't know anyone who has ever done it.
My first thought was that someone was going to use it for skunk deodorizer, although, thanks to Mythbusters, we should all know the cheap, effective way to de-odorize a dog!

(And can I say, it worked splendidly to de-odorize a dog that had wallowed in something dead!)