Who have been the most influential bands (popular or not)?

[XxCaRnAgExX]

To really show who is the most is to create a sort of tree of influence. If you really do make one of these trees (it would be lengthy as hell :/) you would find that you are likely to come up with an influential bluesman by the name of Robert Johnson.
Johnson influenced (among hundreRAB of others) Muddy Waters, who then influenced Chuck Berry, who after that influenced people like the Grateful Dead, the Beatles and the Rolling Stones. The Beatles influence was MASSIVE. With artists like Oasis, Jimi Hendrix and David Bowie (and pretty much every un-death/black metal band ever created since the 70's haha) being influenced majorly by the Beatles. Hendrix helped inspire the metal genre, while David Bowie's image pretty much single-handedly created the glam culture/music. Oasis impact is also large in British music, with banRAB like Muse, Keane, Coldplay and Arctic Monkeys owing something to them.
From there on in you can pretty much branch off to all these other artists which truly shows you the influence Johnson had on music.
Of course there are many other ways you can view the 'tree' with all types of outcomes on who is the ultimate influencer. I just quickly typed some influences and whatnot so of course my branchings aren't really that accurate.

[Silly Puddy]

In terms of making arabitious music, Pink Floyd are by far and away the most influential band of all time. That doesn't mean they are the most out there but I can't think of many banRAB who don't list PF as a favourite at some point.

[Mommy 2 Be(Due 1/25)]

I think Yes and Pink floydwere pretty influential for prog rock.

[Shifty]

I cannot even comprehend that no one has listed Chuck Berry or Little Richard yet. In fact, I remeraber the Rock n' Roll hall of fame cited Chuck Berry as being the closest to creator of Rock n' Roll. For god's sake, Bob Dylan's dream was to join Little Richard, and Jimi Hendrix said he wanted to do with his guitar what Little Richard did with his voice. I really don't think an argument can be made that any one in rock n' roll history has had more of an influence than these two.

[CRX91]

Led Zeppelin
Black Sabbath
Rush
Deep Purple
Pink Floyd
Velvet Underground
Ramones

[GorillazAreLove<3]

David Bowie pretty much set the template for a huge amount of the post-punk and New Wave groups.

[ARMY Brat!!]

The Velvet Underground, Kraftwerk, Gang Of Four come to mind.

[Defy]

On that note:

The Monks
bla bla bla
Discharge
Slayer/Hellhammer (Celtic Frost)
Repulsion/Master/Death/Sepultura/Venom
Releases/More/Amazing/Than/Anything/Metallica/Ever/Released

[j.serabo]

Rock/Metal
Black Sabbath, Motorhead, Thin Lizzy, Metallica, King Diamond, Led Zeppelin

Punk
Ramones, Sex Pistols, Clash

Hardcore
Agnostic Front, Cro Mags, Sick of it All, Bad Brains

I agree with most of the other suggestions like The Beatles but only posted up who i think is influential in the three main categories of music i most prefer