I said "wow" a lot, but probably my first "whoa sh" moment was seeing the intro of Wrath of the Demon for the first time. I had played the Amiga Action demo and was pretty wowed by the game so we got it. The intro scared the bejesus out of very young me (it didn't take much back then), all of a sudden there was an Amiga game with actual murder and blood in the intro.
It unnerves me to see the intro to this day
Amazing artwork.