If you haven't yet played Valve's multiplayer shooter Counter-Strike: Global Offensive then you can now jump in for free—but you'll only be able to fight against bots and spectate games on GOTV.
CS:GO Free Edition came to Steam this week, and it'll be a good starting point for anybody that hasn't already jumped in, giving you a flavour of the mechanics—and a chance to learn the maps—without the pain of getting annihilated in online matches. I'm sure most players that have ever been curious about it will have picked it up for cheap in a sale, but hey, if you haven't, now's your chance for a free taste.
It's still worth playing, too: it came in at number 20 our top 100 PC games list. It's perhaps the purest shooter on PC, with no classes or special abilities and an emphasis on map knowledge and mechanical skill. It's still getting regular updates, too, and recently brought back the MP5 submachine gun.
The full version is £11.39/$14.99 on Steam.