What's your favorite stealth game and why?

[forlik]

My favorite stealth series is Hitman. I like the social stealth combined with abilities of accident-like killing.
The greatest impressions was from first part (Codename 47 in 2000), Blood Money was the best from the best, Absolution was the worst. Yes, for me it's the worst part unfortunately
Also (despite it's not 100% stealth) I like Commandos series very much. Especially the first part with addon (Behind Enemy Lines, Beyond the Call of Duty). I like WW2 setting combined with quite high difficult strategy.
Death to Spies combined two of my favorite series. That's why i played DtS/MoT so much time and spent for modifications even more time than played