I would love to hear your suggestions for unusual things to do in Paris:
Here are mine:
The Catacombs
The Argonaut Submarine museums
l'Espace Dali
The Smoking Museum
The Perfume Museum
I always tell people visiting to do something a bit different. These are just off the top of my head. I would also recommend choosing a neighborhood to stay in like the Marais or Bastille, rather than the obvious center. Too many tourists there!