I'll be flying into Tokyo Haneda at 10:25pm on a Sunday and rather than try to figure out the public transit system that late in the day when I'm already probably going to be exhausted I was thinking I'd prefer to just take a taxi to the hotel. My question is... do taxis loiter around at the airport, waiting for passengers, as they do in the USA?
Yes, of course there are. Depending on where you're going, it may cost you up to ¥10,000 (~US$100) if you board after midnight.
If you're wanting to save a little money on extortionate Tokyo taxi fees there is a direct monorail service from Haneda Airport to Hamamatsucho, cutting the distance required by taxi significantly. Outside Hamamatsucho (the main 'departing to Haneda' station) are a huge fleet of taxis. The monorail is fast and the station is inside the terminal.