The best one to do in Paris are the ones provided by Paris Walks where you can explore just about every area of the city. The tour guides are not only entertaining, but they have interesting backgrounds and extremely knowledgeable about French history.
The weather this weekend is going to be ideal for a walking tour--warm and sunny. l suggest the Latin Quarter walking tour with guide Brad Newfield. Brad packs a lot in, is a great storyteller, and takes you down streets that you wouldn't ever find on your own.
The well priced tours are 12 Euros per person and last about 2 hours. You can pay cash to the guide or pay by phone with Paris Walks. All guides speak English and reservations are not required unless it states to rsvp on their website.