Very strange to think that he'd be 70 now if he lived. The Beatles were the first band I really became obsessed about, annexing my dad's record collection which took in almost all of their albums (apart from, oddly, Sgt. Pepper).
Lennon espoused all sorts of causes during his time - peace, love, avant-garde art, transcendental meditation, but he always seemed to have an ability to cut through all the crap and express exactly what he thought. On the "Imagine" film of his life, there's a clip of a man who had turned up at Lennon's mansion, apparently believing Lennon was speaking to him through his songs, specifically "Carry That Weight".
Lennon, though, swiftly disabused the man of the notion. "How could I have been speaking to you? I've never even met you."
He did record a load of old tosh in his time (Revolution 9, Two Virgins, practically anything after 1975) but I loved him best when letting go and rocking out.