I like the UPS Olympic scheme best.
Although it's the same on the 747, 757, and 767, I'm partial to the 757 since I've worked on it a few times on its trips to GSO. It's kept absolutely spotless. You can run your finger down the side with a white glove and end up cleaning the glove. All other airlines with all-white planes should take lessons.
(I've actually seen "wash me" fingered into the dirt on the sides of other airlines' planes before).