49. Counter-Strike/CS: Source (PC, other versions on X-box, XBL &PSN)

This is why PC gaming is great. A bunch of fans create a Half-Life mod that goes on to become one of the greatest multiplayer FPS ever. Through numerous iterations the game has kept improving and improving. A bit lower than last year because I haven't played it for a while, but with a new version out on Steam, it may creep back up next year.
Clue to no. 48:
A 2D open world game (featuring 512 screens) from the mid 80s. It was released for a whole range of consoles and personal computers, but not any of the current big 3. It stars a character named BLOB.








