Best first track

Jazz has plenty of examples:

Rollins-Saxophone Colossus: "St. Thomas"

Coleman-Shape of Jazz to Come: "Lonely Woman"

Coltrane-Love Supreme: "Part 1"

Brahem, Anour-Thimar: "Badra"

For classical, it is hard to pick favorite opening movements or single movement works, but the following come to mind:

Shostakovich-Piano Trio No. 2

Beethoven-Violin and Piano Sonata No. 5 ("Spring")

Mozart-Vesperae Solennes Confessore

Adams-Violin Concerto

Couple more:

John-Madman Across the Water: Tiny Dancer

Johnny Nash-I Can See Clearly Now: I Can See Clearly Now

Jeff Beck - live at Ronnie Scott’s - Bolero.   Actually entire show is awesome.   Jeff played with Tal Wilkenfeld, Jason Rebello, and Vinnie C.   Great show and you know you are on top when Jimmy Page and Robert Plant are in the audience.  And Clapton sits in on a few songs.

I'm a life long fan of geetar "Classic Rock"

There are some great mentions here.

He's been mentioned before in other threads, I'll do it one more time just because this cut was one of many this 13 year old learned how to play "that sound" on his 1975 Japanese Les Paul copy thru a  cheap transistor amp.

 Side1/Track 1-Stranglehold. Say what you will about ol Ted, he HAD a place in 70's American  R&R history. The album keeps the energy from the lead in to lead out groove.

More, and less conventional listings:

Tonio K- Life in the Food Chain-Life in the Food Chain

PJ Harvey- Rid of Me- Rid of Me

Patti Smith - Horses -Gloria