"The head of Leda" Leonardo da Vinci
Went to see this today, and really no matter what you think of da Vinci (master or over hyped artist), if you are an artist and within 20 minutes of the sketches, you really should go see them :p
Being able to get within less then an inch of these drawings was great, you could see every mark made on the paper, how detailed they were, how tones were made. Glad to have seen them in the flesh, instead of something usually only seen in a photo. Very impressed by the anatomical drawings.
And now I have seen 2 Sargent paintings in the flesh :) Didn't expect to see one in Dundee. I really need to do more research on him, I love how he handles light and fabric.