I love taking the London underground because it's full of advertising. There are posters for musical after musical (there's currently a Ghost musical, f.y.i.) and a whole gamut of ads for art and design exhibitions, events, products, etc, etc… Below is one of my favourites.
Many clients get nervous about excessive whitespace, but this is one ad that undeniably would not work without it!
If you can't read it in the photo to ad goes like this:
Unbelievable value. Das Auto.
I love it! I only saw half of it at first and thought it was an unfinished install, but alas, I squinted to see and someone moved out of the way so then I understood! A great aha moment.