Without a doubt, the hiss that only women make. Guess that's why I like it because it is a feminine sound. Close second? The sound of the stream hitting the water in a toilet that men make. But not coming from a man; coming from a woman that's standing the way guys do. Absolutely HOT! Even BETTER when she unzips (like a guy)m sticks her pussy out, spreads her lips, and shoots a perfect stream aiming it into the bowl.
More and more women pee this way, and I can't wait until it becomes the norm just as it is with guys!