Doom. The first game I ever played over a network. I've played it on PC/SNES/PSX/N64/iPod/Mobile Phones/Laptops/Web Pages and more. I feel I could still sit down and play it all day still. The noise a Cacodemon makes when it dies is unparalleled. I read a couple of the books and the comics and I even quite liked the movie. Doom. Legendary.