Saguaro National Park was one of the first places I visited in Tucson. The saguaros along with the other cacti were always a pretty sight.
While visiting the Pima Air and Space Museum, we had one of the cooler things happen while on our visit. As a volunteer was telling us about the last Air Force One prop plane that LBJ used to get to his ranch that was on display at the museum, Air Force One came in for a landing behind us over at Davis Monthan Air Force Base, as if it was timed. Very cool experience.

Reid Park Zoo.
Even though I had never visited Reid Park Zoo while living in Tucson, I enjoyed taking my son there on several visits to town.
My first year of working at Pearson Educational Measurement, I met a lady that was one of the orignal people to live in Biosphere 2, Linda Leigh. She gave us a personal tour of Biosphere 2 and we were able to visit parts of it that is not open to the public.
Of course, my favorite time of year in Tucson, besides winter, was March because spring training had arrived in town. The Cactus League has the Diamondbacks and the Rockies playing in Tucson.
My favorite places to dine at are Michas Restaurant for Mexican, Frog and Firkin for outdoor dining and Oregano's for pizza.