LAN Parties - It's where Twinkies and kids nicknamed "Chunk" find destiny in each other. A bunch of people with great technological power (usually customer service reps and, surprisingly, LAN admins), hook up all their computers so they can all play the same video game at the same time. Once, a long time ago, a geek realized he had finally made two friends, but he only had two joysticks. Thus, the LAN party was born.
Live Action Role Playing - Watch Queen of the Damned, 4,000 times. Buy a polyester cape from the clearance rack at Spencer's. Hang out at the mall until you're good and angsty (and smell like potpourri). Now, you're ready to prance around town in your underoos and pretend to be a dragon.
Tabletopped Games - It's like your grandmother's bridge club...for basement trolls. You draw up a character sheet, and your Daddy/Mommy (DM) reads you a story. And you roll dice. Did I mention the dice? 4, 6, 18, 32, 64, 128 sided dice. Imagine if your friends wrote "Choose Your Own Adventure" stories. Congratulations. You have just suffered the gaming experience, all while saving countless hours, time, and your precious pride.
The SCA - Where obesity is a sign of wealth and people beat each other with insulated sticks. Yes, it's real. But in all fairness, they don't just go out in the wood like herds of insulated buffalo and beat each other. They also fashion basic garments, forge jewelry, and attempt to make foods and beverages. Fortunately, all of this information is available on the internet and most of the players fund these great efforts through minimum wage jobs, affording them roughly the same level of comfort the "barons" and "baronesses" of olde might have enjoyed. Of course, they didn't insulate their weapons, so 98.9% of this loyal following would have fattened pigs long ago.
Magic/Yu-Gi-Oh/CCGs - For the outcast among outcasts, when you don't have enough friends to tabletop. Some kids save their allowances for years to buy one card which is worth several thousand dollars. What's truly cruel is that many of these players maintain this hobby well into their twenties, pushing the younger generation out of the heavyweight market.