OK, time to unleash the big guns. Here is one which possibly stopped productivity in my office for about a week. There are plenty of games a bit like it, but this is the Daddy of strategic time wasting.

So what is going on here?
Click through to find out about this never ending war.

Actually the war does end, after 100 levels on the old school 1.0 version of DESKTOP TOWER DEFENCE. Its basically Command and Conquer for half an hour at work, with paperclips and slightly cute sound effects. Not that anyone ever plays it with the sound up, that would tell your boss. Basically you place the towers, they fire at the monsters (creeps) you get better towers, they keep coming. You build a maze, they fly over it. Basically it is one of those wonders of simplistic game design that keeps the learning curve just a tiny step ahead of the player, making it satisfying and yet constantly challenging. In writing this piece and getting the screenshots I inadvertently played a quick half hour game.