It would have to be the David, by Michelangelo. I was in Florence and viewed it last summer. It was a breathtaking statue, that shows man in all his glory in terms of the physical body and the unquenching spirit of humanity.

A hard decision to make!  It may have been the fact that we climbed 65 steps (at least) to see this in Florence, Italy, but Michaelangelo's Moses is breathtaking and very inspirational. It is so grand in scale compared to what we expected; having only seen pictures, there is much more to the sculpture on either side of Moses. Amazing. The marble is exquisite, the movement conveyed amazing.

I find Michelangelo's David to be endlessly fascinating, considering how it has endured, and the intricate nature of the work.

Recently I had a chance to visit the Art Institute of Chicago which is home to some of the favorite pieces mentioned above ("Nighthawks" and "A Sunday Afternoon on the Island of La Grande Jatte"). These pieces are both very impressive and I can see why anyone would choose to rank them very high on a list of favorite pieces. Both are large works and explore both style and atmosphere. 

My personal favorites on my visit to this (truly impressive) museum were the Van Gogh and John Singer Sargent pieces hanging there, some of which I'd seen in books before and some I had never known about.

The simultaneous realism and stylized elements of both artists create an almost eerie other-worldly quality, making the paintings alive and active and present in a way that I've rarely seen. 

While I have many pieces of art which I love, my favorite would have to be Georges Seurat's "A Sunday Afternoon on the Island of La Grande Jatte." This piece was created using pointillism (many, many little dots). I am fascinated by the amount of patience Seurat must have had to take on such a task.

I've been lucky enough to visit some of the world greatest galleries--the Louvre in Paris, the Rijksmuseum in Amsterdam, the Uffizi in Florence--as well as many in America. But my favorite pieces are several that hang in my own home depicting local Florida scenes painted by relatively obscure artists of the 1920s.

Right now I'm partial to "The Scream" by Edvard Munch. It's a fun work to talk about in class because it sparks the imagination. Where is this guy? Why is he screaming? What are the other people doing there?

It's hard to pick, but I think that my favorite might be "Nighthawks" by Edward Hopper.  I like it because of the mood that it sets.  It just feels a bit melancholy and lonely and (probably not what the artist had in mind when he painted it) nostalgic.  Hard to explain why you like something, but that's about as close as I can come...