Built in 1959 - steel, glass, brick and concrete - international modern style (Architects: Harrison and Abramovitz).
It was always used as the student center. It was still the student center while I was a student at NYU 1998-2002 and during that time it had that awesome "it came from the 60's" feel. Sure, it wasn't a great building, definitely dated and not always comfortable, but we spent all Thursday nights there at the Sci-Fi Club at NYU, and also occasional Tuesdays for the meetings of the Yo-Yo Club. We had a blast.
It was torn down shortly after I graduated and replaced with a new and more modern Kimmel Center. I'm not a huge fan of the new center - I have no memories there. I have not even been inside of it even once. Whenever I walk by there now, the new student center is a reminder to me that change always happens, whether you want it for not. Nostalgic, a little sad but also somewhat hopeful.