The Special Zone in Sonic the Hedgehog - couldn't work out what the Hell was happening.
Learning what James Sutherland did to his wife in Silent Hill 2.
The gory deaths in The Immortal.
The blue screen of death in Eternal Darkness.
The face stabbing of Manhunt.
The reverse scrolling of Steel Empire.
When the level flips upside down in World of Illusion.
Realising it was myself I could see in Portal.
The first crash of Burnout.
Being lambasted and punched out in Night Trap (yeah, I know).
Getting ribbed by a talking, human-head-having fish in Seaman.
Crazy Taxi.
Finding out I had to press 'reset' to continue the game in X-Men.
Daccat's Island in Eternal Arcadia.
Getting Thunder Force IV to run on my PAL Mega Drive.
Bioshock's opening water texture.
Working out how the Hell Lords of Thunder was running on an 8-BIT system.
Seeing SEGA Rally start to move on the Saturn.
Or Donkey Kong Country on the SNES.
Plus all the MGS, Halo and Mario tricks everyone else's mentioned.