Without a doubt, the chase scene in the original Still Life.
Spoiler:The one that ends on the rooftops, amidst the snow falling, and involving a certain wood plank.
I watched it dozens of times. The video editing in Still Life's cinematics was amazing.
Also, I'll always have a soft spot for the intros of King's Quest VI, The Beast Within, and The Curse of Monkey Island. They all conveyed a true sense of enigma, mystery, and exciting adventure. I will never forget those.