Yes, I saw it. It was a long time ago, at least 30 years ago. Everyone applauded.
My favorite moment was simply being able to attend an NFL game.
It was September 10, 2000. My wife and I were vacationing in Denver, and lucked into a pair of tickets. She, being a native Coloradan, loved the Broncos, but had never been able to go to a game; me, being an NFL football fan from Canada, jumped at the chance to finally attend a game. Off we went.
It was a beautiful, warm, sunny day, at the old Mile High; and the Broncos were taking on the Falcons. I’m a 49ers fan, but I happily joined in with my wife and the Denver fans in cheering for the Broncos. “IN-COM-PLETE!” whenever Atlanta couldn’t complete a pass, which chant is apparently traditional in Denver when such things happen, and made me laugh. Denver won the game, 42-14, which made things great, and we joined other fans in heading out of the stadium to celebrate in downtown Denver.
I’ve seen thousands of football games on TV, but being at the stadium was so much better than watching on TV. So, like I said above, my favorite NFL moment was simply attending a game.
I’ve been to a fair number of NFL games, but my favorite was probably a Monday Night Football game at Arrowhead in September of 2014. The hated Patriots were the opponent that night, and the Chiefs absolutely crushed them 41-14. The crowd set a record for the loudest stadium with a noise level of 142.2 decibels.
That game, incidentally, featured the NFL debut of Jimmy Garoppolo.
I’ve only been to a couple of NFL games, but the most memorable was the same day as the OP’s game - Christmas Eve, 1994. I went with a friend to the Chiefs/Raiders game, which was notable for a few reasons:
1 - It was Joe Montana’s final regular season game. I remember that he threw a pretty long TD pass that most of the crowd around me missed because a big fight broke out in the next section over that got everyone’s attention.
2 - It was the last Raiders game in L.A.
3 - The Raiders set a new NFL record in that game for most penalties in a season at that time. The Oakland Raiders tied that record a couple of years later, and then the Chiefs broke it in 1998. Wouldn’t have know that if I hadn’t had an ear piece in listening to the radio broadcast. It’s kind of not the kind of thing you’d expect to get mentioned over the PA system. However…
4 - Marcus Allen went over 10,000 yards rushing in that game. For those who might not remember, he was a long time Raider who finished out his career as a Chief. There was some bad blood between him and Al Davis when he left, and when it happened there was no mention of it at the stadium. Again, I was listening to the radio so I knew, and I waited for a few seconds to see if there would be any kind of announcement. When there wasn’t I stood up and shouted the news to anyone around me, and at least in that section there was a little bit of an ovation. Seriously, that was a huge milestone at that time, and I thought it was a dick move on the Raiders’ part to just ignore it when it happened.
I don’t think I could perform with so many people watching!
December 1979 at beautiful Veterans Stadium (it may have been a toilet, but it was our toilet) when the Eagles won their first playoff game in my lifetime against the Bears.
My friend and I, both high school freshman, ran on the field after the game to celebrate (because it seemed to be the thing to do). In the craziness on the field, I lost my friend, and stopped for a moment to drink it all in. Suddenly, out of nowhere, I got tackled by my significantly-larger-than-me friend, who knocked me onto the frozen astroturf. He helped me up and told me how I could now tell people I got tackled on the field at the Vet.
The part about the pumpkin sounds innocent enough but it wasn’t. That’s why it was called “The Pumpkin Game.”
It was in the middle of the horrible Joe Walton era. Fans were angry every game. Chants of “Joe must go.” Happened every game. They really sucked.
For about a week and a half in the 80s painters hats became fashionable. They gave out Jets painters hats before the game. In several sections the hats were gathered into piles and burned.
It was near Halloween and someone brought a giant inflatable pumpkin. It was being knocked around the crowd to the amusement of everyone in the stadium. No one was paying attention to the game. Then it accidentally bounced out of stands and on to the sidelines. Someone grabbed it and ran it into the tunnel. The chant went up, “We Want the Pumpkin!” You might think by reading list that it was a fun good-natured chant. It wasn’t. It was angry. It was give us the pumpkin or we will tear this fucking stadium down to the ground. I’ve never felt anything like it before. Apparently stadium personnel Hadn’t either. As the chant got louder and louder, angrier and angrier, they listened. The pumpkin came back out of the tunnel and was thrown back into the crowd. There was much rejoicing.
I’ve only seen three NFL games live, but I’ve had good luck with getting good games.
When I was a kid, my dad took me to Dolphins @ Rams in 1986. Not knowing anything about the NFL at that point I was pretty overwhelmed, and I got to see Eric Dickerson score a touchdown, and Dan Marino throw 5, including the winner in OT. Favorite moment: participating in my first-ever bullshit! chant. 
Chargers @ Broncos in 2008 was a great game. People might remember it for Ed Hochuli’s quick whistle on a Jay Cutler fumble very late in the game, which led to changes to the replay rules for fumbles. My favorite moment was probably seeing a Sproles kickoff return TD.
Chargers @ Steelers was a bit of a runaway for the Chargers. The most memorable play was a wide receiver screen by the Steelers that was ruled a backwards pass, and that the Chargers recovered for a touchdown. The favorite moment of this game for me was realizing that I had better seats than Lynn Swann 
My favorite is a Lions/Bucs game I attended with my dad in Detroit back when I was a sophomore in high shool in 2002.
As a Packers fan, my favorite player ever is a #2 WR named Bill Schroeder. He was eventually released by the Packers and the Lions picked him up. At the time, my dad lived in Detroit and got us tickets so I could go see him play. We did a custom NFL jersey with his name and number (he wasn’t popular enough to have his own jersey sold in Detroit) and I wore it to the game. Not only was he the “spotlight player” in the program, but it was the best game he ever had as a lion. 100+ yards and a TD. The people in my section (especially those behind me who saw his name and number) kept high fiving me every time he caught a ball and the Lions lost (of course) but it was a really good game and a lot of fun.
A close #2 would be the time I won a raffle at work that gave me free tickets (and a whooooole bunch of other free shit) to a Packers game. For $200 I got 2 tickets, free flights, free food, a gift card and some other goodies. It was a down time in our lives (especially Mrs. Cups) and that trip was a much needed joy.