Portal

I wasn't a person who enjoyed puzzle games much, due to there not being enough innovation in any of them. Then I played Portal and I was truly blown away. Yes, the game's length is something that should be considered, even being completable in one or two sittings, taking only three hours. But its what it does in that time that really seals the deal. The portal gun is an incredibly well-designed and very interesting concept, and you'll be hard-pressed to not muck around it at least once in the campaign. Throughout the game, new concepts such as turrets are added in to make more a challenge. The humour is great, with GLADoS' dialogue being written nice, but the game also knows where to stop itself, a large reason why the game is so hilarious. The game looks pretty good for a 2007 game. It's not bad looking by any stretch of the imagination, and you shouldn't be playing this game for its visuals. To rap things up, Portal is a must-play due to its unique take on the first-person shooter genre, and while you might be scared of its short length, picking it up in the Orange Box is a brilliant idea.