Silent Hill 1.
Conker may have been my first actual ESRB rated M game as well. I played Mortal Kombat on the SNES but the SNES version was toned down so idr if it was M or not.It was Doom,
First one on console was probably Conker's Bad Fur Day.
Before the ESRB became a thing, I guess it was Mortal Kombat (the SNES port.) Otherwise it was probably Turok: Dinosaur Hunter.
Eternal Darkness was the first horror game I completed even though it scared the shit out of me, it was a struggle to finish it but finish it I did.Played Eternal Darkness when I was a tiny little baby, I got spooked and stopped playing like 5 minutes in when the roman guy gets turned into a skeleton.
Something something dudes ass in the map editor causing esrb to recall all copies of the game and led to it being m ratedI believe it was Halo 2.
Compared to other games then and now, the Halo games seem relatively tame, so I'm not sure where the M rating came from.