2048

This one's not from the archives, it's timely! 2048 [github] is the latest popular Internet game (you can tell because even Randall Munroe is playing it [xkcd 1344]. And of course, StackOverflow has discussed strategy and said strategy has been automated (a simple minimax approach).

Life moves pretty fast. If you don't stop and look around once in a while, you might miss it.