Without any doubt the concept of the Virgin "Exercise your muscle" advergame has been an inspiration for many of marketers. Now Absolut vodka is online with a bottle search in New York City.
I like it because it's quite challenging (you only have 2 minutes to spot 82 bottles) but most of all because it's artistic, very much in line with the Absolut brand. It's amazing the attention to the details, and I'm always impressed by the work on branding Absolut is able to do also with online marketing. Definitely a reference point for all of us.