Greatest rhythm sections

The rhythm section in a jazz, blues or rock band provides the foundation and motive force for the entire ensemble. The truly great ones not only establish the band's sonic signature, they can generate new styles. Which rhythm sections do you think have been the most influential in their respective genres, and, or changed the way you listened to music? Please try to limit your selections to groups and not individual musicians as it the ensemble sound I'd like to get your comments on.