A no-nonsense genre like punk shouldn't really bother itself with yes-nonsense stuff like intros. Punk songs should slam right in. Most do. A few don't.
Phil's nominated "Smash It Up" by the Damned already, which I'd never heard (the intro, I mean: basically a completely different and rather wet song, nothing like the rousing, ridiculous anthem itself). He also mentions Black Flag.
Here's three others:
Fanfare-knell-salvo, warning of tempestuous darkness to come. The whole song is almost symphonic in its glowering grandeur, but that intro makes me think of Beethoven's 5th.
Just back from Catalina, as it happens.
Were The Only Ones punk? Not really, but "Another Girl Another Planet" belongs to that moment and it has one of the most thrilling ignition / take-off bits of that or any other time, eclipsing the song itself (great as it is).