Dont forget the classics, Eiffel tower, Arc de Triomphe are musts, both shooting from the bottom and the top. These are quick and admittedly not the best shots but just posting as an example. Visited last month. Stayed at the Napoleon (nr Arc de T), but none of the main areas are more than a 10-15 minute taxi ride away from each other.
, on Flickr
^ you can see the Montparnasse Tower, this is a view from midway up the Eiffel tower, quickest elevator in Europe in the Montparasse, should well be worth a visit.
^ one direction from the Arc de Triomphe. Great views from every side of it to be honest.
^ maybe pack a telephoto for a few close ups from up high?
What gear are you taking?
Maybe some street style portraits too?
Personally I'd avoid the Sacré-Cœur and the whole area around it. Didn't really offer anything special and is a bit out of the way, especially if you're only in Paris for the day.
The Court yards at the Louve are pretty impressive, walked there from Notre Dam which was nice, along the river.
Maybe go and get the iconic shots of the padlocks on the bridge?