Hmm, quite a few. I'm pretty old.
-Gale Sayers' 6-TD game at Wrigley Field, December of 1965. I was 12. My Dad got tickets because -- well, December in Chicago. Miserable weather; fantastic day. Fun facts: Sayers would have had a 7th TD that day, but slipped while making his cut to get past the last man (punter) on another return. Also, George Halas kept him on the bench on the Bears' last two scoring drives.
-1983 MLB All-Star Game at old Comiskey Park. Blowout win by the AL after years of NL domination, including the only grand slam in All-Star history (Fred Lynn). More memorable for me because it was the last game I attended with my late father.
There are plenty of others (I used to live a block from Wrigley and saw a ton of games there), but those are the ones that remain top-of-mind after many years.