Hitman: Blood Money, not bad for it's time.
As many others have said, you can go stealth or be ruthless and just rampage through everybody, your call. Does require reading the manual so that you know how to use your weapons properly which I found to be key to enjoying the game. The controls are pretty straight forward, game does have minor replay value as you can try to master the art of the silent kill.
I would recommend this game for your collection as a game to turn to when you just want to ease back from the serious games. To me, it's just a fun game to mess around with.