I was working in World Trade Center #1, on the 95th floor, during the nor'easter of 1992, which if I recall was the remains of a hurricane. It was quite an intense experience; we had the space-saving "rolling file cabinets" that were rolling back and forth on their own, with one finally derailing and spilling files onto the floor (guess who had the job of cleaning it up). Bathroom stall doors were opening and closing by themselves, you could hear a definite creaking from inside the walls, and they were always shutting down the express elevator due to flex.
The thing that was really wild, though, and sadly not to be seen again, was looking out the window and being able to easily make out the other tower swaying as well. I had to keep telling myself "the buildings are designed for this...it's okay!" until it was time to go home.