Experiencing the immersion of the first Half Life game.
Playing WoW, and feeling the gaming equivolent of Hellraiser's puzzle box shooting out dozens of hooked chains to clasp onto my virgin MMOer flesh.
All of Ocarina of Time.
5. Going to a girl's house down the street at least once a week, who I knew from school and who I also knew had a SNES right when they came out (when I didn't have one), just to ask her if I could play it with her. I would always come to her door with a stack of strategy guides and gaming magazines, and she would always say she was busy. I dropped the stack of magazines in a puddle once on my way to her house, so the image of their faded and wrinkled covers were so closely associated in my mind with my failure. They were also damn hard to read once I actually got the system.
4. Playing Ultima Underworld 2, one of the first FPSes I ever played, and felt like I was brought into a whole new world.
3. Playing my first modem-to-modem game of Doom, and subsequently connecting (with BNC cable) my system with another I made from parts from previous upgrades, so I could play my brother/friends in Doom, Heretic, Duke Nukem 3D, Grand Theft Auto, and Rise of the Triad.
2. Playing my first true 2+ player game online, Descent, and realizing that every ship was a different person playing.
1. In my earliest gaming years, going to my neighbor's house, where he always had the latest consoles and the latest games, easily one of the strongest influences on me becoming a gamer.