I used to go to LAN parties. This was years ago, before there was anything better than 56K modems around, so speed was a big factor for using LAN. I was 14 at the time and I played we a bunch of 20-something year olds. We'd stay up late, eat junk food and slaughter each other in Quake and Quake 2. It was great, good company, good games, good food means a good atmosphear. There wasn't enough computers for everyone to play at once, so everynow and then one of us would walk around and watch and learn from the others.
I also played CoD4 at my uni last year. My class didn't play too much, so I went and joined the year above us in their games. I made a lot of friends that year. I became a bit of a prodigy since there was one guy who was practially untouchable for a year in their group until I came around. It was kind of funny since I almost had a white knight thing going on.
I used to play a few C&C games online, CS and WoW online. But I never had as much fun as playing on a LAN. The looks of disbelief, the laughs, no one giving you crap if your not playing your best and no one your not already friends with. Lan is just a really fun enviroment and LAN parties are some of the best parties I've ever been to.