Let's start with the one with the most controversy around it. GoW definitely made a huge splash with the unique combat system and context-sensitive segments, so much that every developer that wanted a good game would resort to this style, including Capcom (RE4).

The greatest sequel to the greatest game. More blood, kills, and overall heart-stopping violence. If you do not whoop every time you kill someone, this is not the game for you.

From a blunt club to a Stun Club. Where will I go next? Not exactly big now, but a great title for 5 bucks at your local Gamestop.

The game that sparked a legacy. tPL uses a great mix of platforming, action, and humor that is not horribly rude.

Yay! Stealth! Blood! Oh, sorry. *whispers* You have to be quiet. The terrorists might hear you! Great game, especially to the newcomer to the genre.