Which Games Totally Blew You Away/ Delivered The Goods?

[Reasonable]

Classic Adventure
Battlezone
Elite
Doom
Ultima Underworld 2
Tie Fighter
System Shock 1 & 2
The Thief Series
Deus Ex
Grim Fandango
Half Life 1 & 2
ICO
Shadow of the Colossus
Splinter Cell
Silent Hill 2
Call of Cthulhu - Dark Corners of the Earth
Portal
STALKER
Oblivion & Fallout 3
Uncharted 2

Some are buggy, but all had at least one element, mission or 'feel' to them that made me sense just how amazing the videogame format could be. I'm sure I could think of more, and a whole generation of console games I never indulged in at all - for those amazed at lack of Zelda, Mario, etc.