...wait for it...
"When one is tired of London, one is tired of life, for there is in London all that life can afford." - Samuel Johnson
I was blown away by the original. With its tricks of perspective, including the use of the (skewed) mirror image behind the barmaid, the painting is at once beautiful and completely disorienting. Seeing it solidified my respect and admiration for Manet.
I think it's probably still my favorite because it made a huge impression on me during my first trip to London when I was in college (almost 12 years ago).