That sad scene where your favorite character dies, that zombie that popped out from nowhere which made you jump like hell, that hilarious moment that still makes you laugh even if its been like 10 years, that awful puzzle that still haunts you, that unbelievable goal, that wacky glitch ... you know
Here's a few memorable moments (for me):
Secret of Monkey Island - The "Oh dear, you are dead" screen followed by "Rubber tree".
Final Fantasy 7 - When Rufus (my FF7 favorite character) kills Weapon and Weapon counters, killing also Rufus. Cool moment imo. You can watch it
here.
Ecstatica (Loved this game) - The many times when the werewolf beats the living crap out of me
. Watch it
here. (one of the memorable moments i speak of: 5:15 - 5:40)