If you can stand the repetitve gameplay, give it a shot.
Manhunt is pure and simple a stealth game. Cash, the protagonist, can fight hand-to-hand, but the game is intended to be placed in stealth mode. Some of the stealth killings are indeed intense and gruesome, but after about 5 missions they become less shocking. The game primarily consists of distracting an enemy, finding a hiding place, sneaking up behind him, and executing him. Wash, rinse, repeat. Some people are going to like this, and I must admit that the brutality of the kills is morbidly fascinating, at least at first. However, this kind of gameplay has been done much better in games such as Hitman. If you can stand the very repetitive nature of the gameplay, this might be worth checking out. Otherwise, try something like Hitman: Blood Money or one of the Splinter Cell games instead.
Pros
+Good idea for a game
+Some truly over-the-top executions
+Good voice acting
+Typical controls for this sort of game
Cons
-extremely repetitive after a while
-merely decent graphics
-not enough tension
-little character development
-the checkpoint save-game system