My all time dont miss-it-even-if-hell-freezes-over is....
Prototype (Adventure scifi 3rd person)
Prototype for PC - Prototype PC Game - Prototype Computer Game 
I dont want to ruin the fun and i disagree with gamespot's rating but i say.GET THIS GAME.I usually never play the same game twice.At all.But this was the only exception i ever made.
About
: The story revolves around Alex Mercer,who doesnt have any memories of his past.However, he has these sick powers which can transform his arm into a blade or a whipfist (you know prince of persia?) etc.Its a game of mass destruction and mayhem where manhatten has been affected by a zombie outbreak due to a virus
My personal list. (Games ive played that are outstanding)
Dawn of Discovery Dawn of Discovery for PC - Dawn of Discovery PC Game - Dawn of Discovery Computer Game 
How do you create an entire civilization from a boat in the middle of nowhere? Yup thats whats this game is about.Its a really grand scale game that people who prefer to design,rather than destroy should play.
Assassins creed
Historical 3rd person adventure assassination
If you've never heard of this game...idk what to say.Its a really fun sandbox style game revolving around the assassin Altair.This game changed the dimensions of gaming and created the genre that spawned many games like prototype.
Burnout:Paradise
GTA meets burnout.I dont have to say anything more haha
Games suggested by fellow animecrazier's
Red faction:Guerrilla (Idea by naitsirk0)
Red Faction: Guerrilla for PC - Red Faction: Guerrilla PC Game - Red Faction: Guerrilla Computer Game
Street fighter IV (Suggested by TheLoot)
Street Fighter IV for PC - Street Fighter IV PC Game - Street Fighter IV Computer Game
Other than that,
notable mentions are:
Batman: Arkham asylum (Adventure detective)
Red alert 3 (strategy)
Elder scrolls IV,Oblivion (RPG)
Fallout 3 (RPG)
Future to be released games that you should get:
Assassins creed 2
Dragon age origins