What's your favorite painting/artist and why?

[T4Texas]

Even the least artistically informed person has probably looked at a painting somewhere and said "Hey, I like that" to themselves. Art moves us in ways we sometimes don't even realize. So old or new, whatever style pleases you, tell us about some of your favorite artists or paintings and why they made an impression on you.
I will start by saying my favorite is Edward Hopper. He painted cityscapes and rural scenes usually devoid of people and was active from the turn of the century through the 1960's. I like his paintings because of their emptiness and even when they do have a person in them, it still seems to set a mood that you can imagine looking into the windows of the buildings he painted.