There is some mighty good stuff already posted in this thread.
Myself, I’m a big fan of American Regionalism and its offshoots.
Andrew Wyeth’s
Christina’s World probably tops my list. It has fascinated me since childhood, and my wife gave me a very large framed print of it for my birthday one year. It has hung In our living room ever since. There have been countless times when I’m walking through the house on the way to doing something else, and I’ll stop for a moment and study it even more.
For me it elicits much of the human condition; drawing on both despair and hope, obstruction and determination, and how one’s own world can be incredibly small and yet massively expansive at the same time.