Football - '98 win over Arkansas. That last drive to take the lead was one of the most memorable sporting moments of my life. Honarable mention goes to the '99 Egg Bowl. The pick and kick was one of the best finishes to an Egg Bowl ever.
Basketball - '96 SEC championship win over KY. The KY team is regarded as one of the best to ever play the game and when we took them down, I remember having one of those "holy ****" moments when I realized how good our team really was.
Baseball - Burke Masters, end of story.
Golf - I feel for the guy, but for some reason the Jean Van de Velde collapse at the '99 British Open is by far the most memorable moment that I can think of. Needed only to make double bogey on the 18th on Sunday to win, but he hits it in the creek and ends up with a triple to force a playoff where he then loses. Unbelievable.
Racing - Dale Earnhardt crash at Daytona
Xbox - I was the house champion of NCAA '03 football and while we never kept up with records, I had to be somewhere around 200-0 at the time. Anyway, a roommate had me down 35-24 with under a minute to go and seemingly the entire Academy Village complex was there to watch me get beat. I can still remember my roommate not even being able to sit down from the excitement of kicking my ***. Well, he was blitzing nonstop so I ran two straight quick slants across the middle and scored with about 10 seconds to go. Everyone knew that my only chance was going for two and to somehow come up with a field goal, so I did go for two but the play failed. Once again, the place went crazy. I lined up for the onside kick and one of his guys actually recovered, but I pounded him as soon as he grabbed the ball and it came loose. I recovered somewhere around the opposite 45 yard line with 3 seconds to go. Rather than go for a hail mary, I did the craziest thing that I could think of and just threw a quick screen to my tailback as soon as he crossed the line of scrimmage after the snap. 55 yards later and with time running out, I scored and won the game as a controller went smashing into the wall. Best moment in video game history for me.