The one that always stands out for me is No Way Out 2004: Eddie Guerrero beats Brock Lesnar.
That one is probably more of a personal favorite because I wanted Eddie to win so badly, but it was nice to see other people did, too. That was a great crowd, and they popped like a helium balloon when Eddie got the three count for one of my most favorite moments in wrestling history. It was impossible not to like Eddie, and seeing him at the top was worth the pop.
Also, the RAW when Austin broke up Taker's attempt to marry Stephanie. That was a pretty messed up moment in wrestling history, considering all the things that it was suggesting, but that crowd erupted when Austin's music hit. I also feel that in a creative sense, that was one of Austin's greatest moments. I would argue it's when Austin became fully recognized as a face. Sure, he hated VKM like cancer, but he couldn't let a young girl be treated like that. It showed that Austin had a heart and made him even easier to cheer for.
There have been bigger pops all-time, but those are the two big pops that I'll never forget.