Here is my list, in no particular order:

1. Have a picnic lunch in Luxembourg Gardens.  I buy my sandwiches near the Odeon metro then walk down to the gardens.
2. Have a picnic in the Gardens at the Cluny Museum.  This is the one time a year I buy myself a "#1" (Big Mac, fries, soft drink) at McDo's and then enjoy it immensely in the quiet gardens in the center of the Latin Quarter.
3. Take a cruise on the Seine.   Nothing shows off the City of Light better than this.
4. Sit at le Cafe Petit Pont.  Outdoors.  Gazing at the beautiful scenery of Notre Dame with a glass in hand, and jazz in the background.  What is better than this?
5. A cruise down Canal St Martin.   Loll down the canal passing through some of the prettiest neighborhoods in Paris.
6. Hit a flea market.  I like the one at Porte de Vanves.
7. Take in a Jim Haynes Party.  Sunday night at his place.  The crowd spills outdoors.
8. Spend an afternoon at the le Square du Vert-Galant at the tip of the Ile de la Cité.
9. Go to the Marais, grab a fallafel at L'As du Fallafel and sit down on the steps of the elementary school around the block.  Pure ecstasy.
10. Take a Velib bike ride on a Sunday morning, heading in no particular direction.