I have been waiting for a post like this for a while. These are some of my favorites. I love Sargent and Freud, I would kill to be able to paint like them, sadly, I must practice some more--paintings aren't quite at that level yet.
Sargent - Gassed
Sargent - Madame X
Freud - Man in a Chair
Eakins - Max Schmitt in a Single Scull
Hopper - Early Sunday Morning
You know you're not doing anything, go to artchive and look at these, they are beautiful paintings.