One of my favorites was the Beatles "1-2-3-4" intro to "I Saw Her Standing There"."
With due respect, that's a joke right?
No, it's not. That is part of the intro to that song, and it sounded so cool that they left it in the recording, and always included that in their live performances of that one song. It is an integral part of the intro, and most people would not even try to leave a count-in like that in a recording (cause they usually don't sound that great), but it became a memorable part of that song (which was rated #139 in "Rolling Stone's" greatest 500 songs of all time). (For an explanation of why producer George Martin decided to include that in the release, see article
"I Saw Her Standing There".)
In the second clip I provided, you can see how much fun artists like Mick Jagger, Bob Dylan, George Harrison, Billy Joel, Bruce Springsteen, Brian Wilson, Ringo Starr, Ronnie Wood, Les Paul, Neil Young and Jeff Beck had doing that song during the Hall of Fame induction ceremony. (They had a guy doing the count-in on that "superjam" version too, but it wasn't dramatic (and cool), like Paul McCartney did it.)
You can also watch that superjam version here.