1- The Beatles- starting the British Invasion, making the rock band bigger than the Elvis types in rock music, songwriting, recording technology, Pop Music, Power Pop, Folk Rock, basically revolutionized Psychedelic Rock, electric 12 string guitar, Progressive Rock, early Metal "Helter Skelter", and many exotic instruments like the sitar, tamboura, tabla in rock music. Lastly with Tomorrow Never Knows they began experimenting with tape loops, musique-concrète, and effects which were crucial to the development of modern electronica.
2- Jimmy Hendrix- revolutionized guitar playing in all genres, hard rock, blues rock, jazz rock and psychedelic rock.
3- The Kinks- bringing raga influences in Rock, one of the cornerstones of the British Invasion, hard rock, proto-punk, songwriting, Britpop, and using guitar distortion.
Those are my choices. There is more to rock than hard rock or heavy metal. I like Zappa also but his influence in not really felt in mainstream music IMO. I like Led Zeppelin I think their influence is really hard rock and some metal.