Obviously that's a highly subjective thing but here's one that should probably belong on a short list of the best out there. I'll let Martin (Rakey on MINI2) explain for himself:

roof

A cold winters night in the pub with my mates in December 2002, told them I had test drove a MINI cooper S, and wanted one, but wanted to something a little different. So we sat, drank a few beers, and decided in homage to my previous mini cooper, it should be black and white, then I felt this was not enough. So talked about how I could make it totally unique, and we came up with hundreds of ideas for the car, roof graphics was the main area of discussion. My final choice was made, a classic iconic image of my favourite actor.

Well a few people knew I was planning this, but here it is finally done and on me car. I would like to thank them for their encouragement and support (you all know who you are), but a big thanks has to go to Mad Brummie for putting me intouch with Russell at Action Graphics.

(this was originally posted on MINI2 and has been reproduced here with permission)