Sorry. Can't name just one. I have to agree about Peter North. But Lucas Ridgeston has had some very impressive ejaculations also. In one of his early Bel Ami flicks he has a scene where he fucks Johan Paulik and then pulls out and jacks off to orgasm. You can count 13 actual "shots" of cum plus some additional dribbles after that.
Also, there was an actor in the 1983 William Higgins film "Sailor in the Wild" whose name I don't know. I never saw him in any other films. He had brown hair and a massive, extremely thick and veiny cock. There was a scene of him masturbating on a rock. When he ejaculated there was an amazing amount of semen. I would seriously estimate that he shot about a third of a cup of cum.