10. Black Mesa
Technically, this is a Half-Life 2 modification, so I debated including it on the list but ultimately decided that the project, which has been hotly anticipated since 2005, was of a high enough quality to stand comfortably alongside any of the games on this list. Just consider how massive an undertaking a remake of Half-Life would be and how, even after eight years in development, people all over the place were eagerly anticipating the games release enough that the severs overloaded minutes after the game was made available. I had to wait for two hours just to get the chance to download the mod. Of course, hype isnt everything, but luckily Black Mesa avoided becoming another Duke Nukem Forever by giving us the touch up of the classic we always wanted and not trying to fix what wasn't broken. The modification is fantastic and beefy enough to be its own game, yet its 100% free as long as youve purchased a source game. That. Is. Insane. Black Mesa will go down as one of the best love letters ever devised in the history of gaming deservedly so. If you havent gotten the chance to play Half-Life yet for whatever horrible reason, now is the time to do so with this mod. And even if you have, its worth the trip back. Now go. Theyre waiting for you in the test chambeeeeer.