After you walk through a torii at a Shinto shrine, you may encounter something like this:
This sink-of-sorts is for people to wash their hands and their mouths before going to the shrine.
If you're a germ freak, you might want to just wash your hands since a lot of strangers' mouths have touched the cups. Personally I just poured water into my mouth without touching lips to tin. I then -- per Paula's instructions -- did a little rinse and spit.
I think the tradition and symbolism of this act is pretty cool. I can't tell you how many churches in Europe and temples in Southeast Asia I've gone to, dripping with sweating from walking around and probably breath reeking of lunch. To me, this simple cleanse is a nice way to show you're entering somewhere special.