Song intros that really grab you? ?

Most notable one chord (if you wanna call it that) intro! - Hard Day's Night.

Bruce Springsteen: NYC Serenade and Something in the Night

Opalchip, great call. A single memorable chord. At the other end of the spectrum, I'd nominate the improvised tenor sax and drum intro to Steely Dan's "Everything Must Go." Glorious playing, and really contributes to the meaning of the song (those guys are brilliant).

On a different note, the intro to Curtis Mayfield's "Pusherman." That is _so_ cool.

"Darkness/Earth in Search of a Sun" - from First Seven Days by Jan Hammer.

"Toccata and Fugue in D Minor" Bach. played by E. Power Biggs

Beethoven's 5th has been grabbing people for several hundred years.