List your top 10 games of all time

[Tintin]

Thief Gold
Thief 2: The Metal Age
Age of Empires 2 and expansion
Impossible Creatures
Psychonauts
The 'Worms' games
No One Lives Forever 2: A Spy in HARM's Way
Amnesia: The Dark Descent
Half-Life 2 and expansions
Portal

(I'm currently working on Planescape Torment - it might make the list)