Some guy posted on the classics board about X-Men 189 from 1985, which shows a future with a destroyed World Trade Center.
He was wondering if that would make it worth something. It doesn't, of course. But that jogged my memory about other times when these iconic buildings have figured heavily in Marvel comics and were even damaged or destroyed. It's kind of inevitable that they would come up when most of your stories are set in New York.
The most notorious is probably in the adjectiveless Spider-Man 16, when during a crossover involving X-Force Juggernaut apparently knocks one down.
I also remember that in the first issue of Damage Control a giant robot falls and lies sprawled between them. Wish I could find an image.
So, any others? Please describe them and post images if you can. Not just times when they're damaged, just when they played a major role. We should remember the positive impact this important landmark has as well as the tragedy. And I don't think I have to tell you to be sensitive about it, it's still a horrible thing. I'm just interested in seeing and discussing how it was portrayed in Marvel comics over the years.