Metal Gear Solid
-Meeting Revolver Ocelot.

Yes, yes, it might not be an action packaged or very emotional moment, but meeting the guy for the first time, who has a huge impact of the whole story and appeared in EVERY Main Game, it sure is nowadays a moment to remember, when we see him the first time playing with his Revolver.

-Psycho Mantis

Yes, of course. Mantis could read your mind and broke more then once the 4th wall. Pinkie Pie would be proud.

-Meryl gets shot

Short after the fight with Mantis and clearing a cave with wolves, they reach the underground way to the towers. After clearing a little mine field, Mery get's aimed by Sniper Wolf. Before both realizing what's going on, Meryl get's hit. Trying to fight back, she just get's shot more. She then tells Snake, that he should leave to find a way to beat her and to believe in humanity. The player has no choice but to leave to get a PSG-1 Sniper, or Wolf keeps shooting at her, until she dies.

(Scene from the remake)

-The torture

After seemingly getting revenge for Meryl, Snake continues his way alone, before he got in an ambush of Wolf. Knocked out the next thing we see is tied on an electrical torture bed. It's also the moment, where to decide to try surviving(Good ending), giving up(Bad Ending) or failing(Game Over, starting from last saved moment).

-The Tower fight

Everypony probably remembers it. Passing a door in the tower and the camera spots us unvoidable. And so a run starts, fighting your way to the roof.

-Death of Sniper Wolf

After fighting her again, Snake this time really beats her. With a deadly shot, she wont live long anymore. The scene has more impact when watching or playing yourself. The end leaves a dead Wolf, a sad Otacon and a Snake who continous his mission.

-Naomi's story

During they pal card activating progress, Naomi calls Snake, telling about her reasons and her past. Snake finds out that he kindadestroyed her life and that's why she wanted revenge on him, what happened with the FoxDie-Virus, Snake has in himself.

-Metal Gear Rex Fight

A Metal Gear game without a fight against a Metal Gear? Impossible, if we keep the very first MG out of it. And so Snake has to fight again a Metal Gear, controlled by his own clone brother Liquid. A hard fight, but satisfying when beeing succesful.

-Gray Fox Death
After round1 of the fight is done, Gray Fox appears to help destroying Metal Gear. However he get heavily hurted and after an emotional moment, where Snake cant pull the trigger, we see him die in a really painful way. But Snake will get revenge

-Fight with Liquid Snake

Finishing Liquid in under 4 minutes on a small high area? Yep, that happened. And Snake kicked him down.

-Meryl's Death(Alternate ending)

If we gave up the torture, we seeing a sad scene, where Meryl dies.

-The Escape

Snake and Meryl fighting their way out of Shadow Moses, before it get mobed into hell, including stopping Liquid once and for all.

-A new future

With a happy end we see Snake and Meryl driving away, mission suceed.

... at least until MGS2, dun dun duuuun.