The Beatles, "A Day in the Life." Greil Marcus once wrote, "[A]t the time it was obvious that Revolver, released in 1966, was better than Rubber Soul, just as it was obvious Sgt. Pepper was better than both put together. The times carried the imperative of such a choice—though it was not really a choice at all, but rather a sort of faceless necessity. The only road, after all, was onward." And "A Day in the Life" was the exemplar of Onward. He added, "Such a choice does not seem so obvious now, and of course the necessity has faded."
Aretha Franklin, "Respect." The Acclaimed Music site lists this as the #11 track of all time. That seems off ... of the top ten, only "Like a Rolling Stone" and "Johnny B. Goode" strike me as the equal of Aretha's greatest hit.
The Jimi Hendrix Experience, "Purple Haze." Perhaps lost in the greatness of Hendrix's guitar work is the fact that he was also a great vocalist and songwriter.
The Doors, "Light My Fire." I remember once, in the early FM years of Tom Donahue, he said he didn't want to play this song because they played it all the time on the AM dial. Listeners pointed out to him that they didn't listen to AM any more, so they never heard it. The version in the video is the short one, with a different Morrison vocal.
Jefferson Airplane, "White Rabbit." I wouldn't have said it at the time, but this is just about a perfect record. One reason is Grace Slick (see below).
The Velvet Underground, "I'm Waiting for the Man." Many of these songs elicit memories of the 60s. This is the only one that personifies those times as standing around waiting for your dealer to bring you heroin.
Nico, "These Days." That's Jackson Browne on guitar. He also wrote the song. He was 17 when this was recorded. He loved Nico. She was older than 17.
Love, "Alone Again Or." Arguably the most famous song by Love, the band led by Arthur Lee. But Lee didn't write it ... that was Bryan MacLean. (As with The Kinks, I preferred the raunchier Love of their first two albums.)
McCoy Tyner, "Four by Five." Tyner, Joe Henderson, Ron Carter, and Elvin Jones.