Fraps is a perfect freeware for anybody who is completely into games all the time. This software lets you benchmark any of your games, using DirectX or OpenGL graphic technology, by letting you calculate frame rate or FPS and save it to your hard disk. This will help you when you compare it with other games and do benchmarking test.
Apart for benchmarking and FPS you can alos record video of the game you had been playing or take any particular game scene screenshot which you would like to keep it as rememberance or would like to put it across in forums. Here is a sample of youtube video which was created using fraps for WOW game
However with this free part of software you would get watermarks and limitation on how long you can record a game. so if you are not looking for commercial usage where watermarks give trouble then its all good to use. Find more about Fraps