Couldn't possibly pick just one! I consider the Beatles and the Stones two members of the "Trinity" of Rock and Roll (the Doors being the third). I love the bands mentioned in the poll and the others that people have mentioned in their comments. Whatever you may think of the Sex Pistols and Judas Priest, you can't deny they set the tone for punk rock and heavy metal, respectively. And being a child of the 1990s, I love Oasis and the Verve.
Oh yes, can't forget Queen and David Bowie!