Maybe it’s a boss fight, or the conclusion of an amazing cutscene. Maybe it’s the moment a game ‘clicked’ with you, or the moment you and the game combined for a moment you’ll never forget.
Far Cry 3 had a couple. Burning the weed fields is memorable. Destroying the base and escaping in a chopper while Flight of the Valkyries plays was so fun.
The Last of Us’s opening sequence. That leveled up the industry as a whole for acting and writing.
The final scene of the first disc of FFVII. That scene plus the realization we have no healer in the party will last with me for decades.
Halo: Combat Evolved - right at the end of the training phase: (paraphrased for emphasis)
“Master Chief, the ship is on fire, disabled, being invaded by a huge coalition of hostile aliens, and on its way to crashing into a mysterious planet-sized artifact. We are in the middle of nowhere, and no help is coming. Here’s our computer core. If the aliens get their hands on it, all of humanity will perish. All I can offer you in support is my ceremonial service pistol and one clip of ammo. But this is you I’m talking to, so I imagine everything will turn out fine.”
Stepping out into the wasteland in Fallout 3 for the first time. Say what you will abour Bethesda and bugs, but they know how to put on a show.