As far as classical art, the first painting I remember being moved by was by Spanish artist Francisco Goya. I was thumbing through a book of paintings and came upon a page I could not turn away from. I was a child at the time and didn't have any idea who painted "Saturn Devouring His Son" (shown right), or the meaning of the art, but I felt deeply disturbed and captivated by the image.
Goya was a court painter of great skill, though his "unofficial" works are more interesting to me by far. Like Kollwitz, he lived through a time of turmoil and war, which was reflected in his work. He is known for his scenes of violence, especially those prompted by the French invasion of Spain. A serious illness in 1792 left Goya permanently deaf. Isolated from others by his deafness, he became increasingly occupied with the fantasies and inventions of his imagination and with critical and satirical observations of mankind.
In relation to my own art, you can see how his heavy use of shadow and social commentary influenced me. Goya's use of the title to add more depth also inspired me, such as in "Hunting for Teeth" and "The Captivity is as Barbarous as the Crime" (shown as last two images below).