Halo Combat Evolved
Without mentioning other games that have entered the market (such as Gears of War which I hear is also great) Halo has been around for years, and it is a staple of college campuses, dorms, bedrooms, basements, family consoles and gaming cafes. It’s a favorite of many a console player (think Microsoft's Xbox) as well as PC and MAC players, and for good reason. It is an exceptionally well-made, fun and great game. If you haven't tried playing Halo yet, maybe you should try it.
Most of the fun stems from the fact that the multiplayer online matches unfold in ways that you can never predict, and you always get actual human beings at the other end of the controls, and that is almost always entertaining. Start with single player, then later try online matches or even a LAN party with your friends. The science fiction back story of the Covenant and sprawling maps combined with stunning graphics make for a jaw-dropping immersive video game experience in the single player mission mode also. But this is just part of it—you add to this a variety of fully-equipped vehicles, jeeps with guns and the fun really starts happening, and I’m not even mentioning the freaky menace of aliens that you encounter along the way. I have logged hours and hours on this game—probably in the hundreds of hours, and it’s as fun as any game out there, and with the added benefit that you’re not stuck playing the against the computer and it’s AI. It’s no wonder the Halo multiplayer demo is still popular online even after all these years.
PC download available at: http://download.cnet.com/Halo-Combat-Evolved/3000-7441_4-10235611.html
Mac download at: http://www.apple.com/downloads/macosx/games/demos_updates/halocombatevolved.html