I realize not everyone can get to them, but the facilities at Club 33 are ona par with those at Google HQ. Having used both, I can say that while Club 33's do not have heated seats, etc, they do have a much better ambience. Not to mention location, location, location!
The one in DCA right next to the wine tasting. I have never seen anyone besides myself go in. It's really nice but kinda creepy that hardly anyone uses it. My other favorite is the Hungry Bear since it is pretty big and still pays tribute to the Country Bears.
What is the big deal with the "secret" bathroom?! It's in the hallway going to Rancho del Zocalo. I really don't think it's that big of a secret just because it's not on the guidemap. I mean, honestly, how many people look on a guidemap for a bathroom?
My favorite restroom is the park is the one in Adventureland, I mean, sure it's over-crowded, sometimes not 100% clean, and you can't always get to it because they make you go all the way around Frontierland to get there... but the MAIN reason I love it is because you can get a Fast Pass for it and come back hours later when you really really have to potty. By the way, I don't think the Fast Pass for that bathroom is on the network, so you can pee there AND pee at another of your favorite attractions.
I love the Indiana Jones themed one. Not many people know about it, but it's really awesome. It has like three stalls, each themed like the three doors on Indy. It's really fun if you know where to look.