I have numerous favorite gaming moments. 

My Saturday afternoon marathon of DOOM II that resulted in me being locked in the University Library.  My first time firing up Half Life (though that game makes my list of all time game disappointments as well).  My first time playing the full 3D of Descent II (boy, I would get dizzy playing that one).  The final cutscene of Starcraft.  Reverting from hyperspace to see Kharak burning.

But one moment tops them all.

Finally dying.  And knowing I wouldn't be coming back to life.  Shaking off my immortality, discovering my true identity, and no longer being The Nameless One.  Planescape: Torment.

When I played it I had never really played a Dungeons and Dragons RPG.  I didn't really know anything about the setting, the story, the mechanics of the game.  I just found it for a good price, decided to give it a try, and slogged my way through it until I understood how to play.  And I became engrossed.

Planescape: Torment had more emotion, more passion, more intrigue, more wonder than many epic books I have read.  The characters were brilliant, the choices felt important.  The story was fascinating.  I relished every line of text I could read (and anyone who has played it knows there is a LOT of text in Planescape: Torment), looked forward to the next revelation of who my character was and what brought him to his current state.

And to finally reach the end, wrap up all the loose ends, discover the secrets of my traveling companions, and accept my fate in the Blood Wars, well, it was a cathartic experience.

Games that great are hard to come by.  It isn't often electronic media can connect with the player on such an intellectual and emotional level.  Planescape: Torment did that for me.  It is, without doubt, my greatest gaming moment of all time.  Anyone want to share theirs?