This is a hard question. I started paying attention to Iowa State games in the early 90's. I was at the 1986 Michigan, but don't remember much so I can't really count that.
Several standout:
1. Oklahoma State 1992-I was 12 and I was TICKED OFF when they were down at halftime. The comeback was amazing. My mom, because she is awesome, started taping the game when the comeback was on, so we had about the last 10 minutes and the OT on tape. I watched that so much that I had it pretty much memorized. Even now when I see clips from that game, I can tell you what the announcers said before and after the clip that they show.
2. Iowa-1999. This was in Larry's 2nd year and Alford's first year. Alford was getting a lot of hype and we had no idea that Iowa STate was going to be any good. It was my junior year of college and the first thing I remember is a really drunk girl threw up a few rows in front of me. Iowa State played really, really well and after the game Fizer marched around with a "Eustachy #1" handmade sign (that he said he asked a manager to make at the first timeout). It was fun after yearing for a long time about how great old Stevie boy was going to be.
3.2001-Kansas. We won. Don't remember much of the game, but do remember waiting in line outside on a cold day at 6:45 for a 12:45 game.
4. 2012-Kansas State-I had to miss the Oklahoma STate game a few weeks before (the Scotty banked 3). It was fun to see a big comeback (I think they were down 14 in the second half) and a last second win. Also the Baylor game last year....there was such hype for that game. I think they oversold tickets and for the first time in recent memory there were NO empty seats. The hype for that game was just unreal.
I'll just add that it kind of snuck up on me before the Baylor game last week that we have a pretty special Hilton streak going. It's one thing to say 20 games in a row, but when you really think about it, it is really impressive and hasn't happened much at Iowa State. And on a personal note, it means that I have left Hilton happy for over a year. After years of leaving Hilton after a heartbreaking loss (against good teams!) in the McDermott era it is nice to leave happy.