The last truly touristy thing I did in Paris was take in one of the Bateau Mouche tours. The basic run down is that a really big boat (with a lot of people on it) sails up and down the river in Paris, and tells you a bit about the the history on either side. My guide book describes taking one as the "only way to get away from the obnoxious noise" of them.
I didn't find the noise obnoxious, just remarkably pointless.
The annoucements (when you could hear them) were in three languages (French, English, and Spanish), and usually by the time you could understand what was being said, you were past the thing you wanted to look at. The one I took was quite uncomfortable to sit still on, as well.
But, ignore that, it was fun. I took it last time I was in Paris, and it was interesting to take it this time. For example, there were a lot more people this time. (Of course, last time, it was early Spring, and this is the heart of tourist season. I've been told that any Parisian who can afford it heads out of Paris for the summer to get away from the heat and the hordes of tourists. I can completely believe this - the heat is oppresive. I won't go into the tourists.)
It was quite relaxing, since I had spent most of the time I was in Paris walking everywhere, and this gave me the sense that the interesting stuff was coming to me. I tried to take some pictures (not many - I just finally gave up because the boats do move quite quickly, but a few photos managed to look nice), but mostly I just tried to enjoy the views.
There was a lot of waving at people on the bridges (which was fun), waving at people in other boats, and generally being silly. I made a valiant attempt to speak French to a pair of little girls that were running around playing tag on the deck, but one of them assured me quite seriously that she only spoke French, so she couldn't understand what I was saying. *grin*
Would I recommend it to someone else? If they had time, and wanted to relax a bit while looking at the city. I'll admit, the tour made me think "Damn it, I missed that!" a lot, and afterwards had to remind myself that, for only being in the city for a couple of days, I made a very good run at seeing the things I wanted to see. And, as I keep saying, it's not going anywhere. I could hop on a train and be in Paris tomorrow if I really wanted to.
The whole thing was tinged with a bit of sorrow, though, since I figured that my adventures were done.
I'm so cute when I'm wrong.