Texas game at Gampel 2010. The Kemba 3 already mentioned, and a Stix alley oop in the first half when Dyson threw the pass from half court were the 2 loudest moments. That, and what seemed like an endless streak of Texas turnovers and fast break layups. I thought this crowd was significantly louder than the Syracuse Gameday game a couple years later, but to be fair for Texas I was sitting in the 5th row or so of the student section, and Cuse I was in the top few rows, so that may have made a difference.
If you count watching the championship game in Gampel then doing that in 2011 was the loudest I've been to, but I don't think that really counts.
MSU game at MSG.
Those are the ones that stick out for me. I'm sure Shabazz against Florida was up there but I wasn't there.