Vincent van Gogh painted over thirty self-portraits during his lifetime; these two, from 1887 and 1888 respectively, have long been my favourites:

“I purposely bought a mirror good enough to enable me to work from my image in default of a model, because if I can manage to paint the colouring of my own head, which is not to be done without some difficulty, I shall likewise be able to paint the heads of other good souls, men and women.” — Vincent van Gogh, letter to Theo van Gogh, Arles, c. 16 September 1888