Johnny Cage would probably be my main choice. But Mileena, Shao Kahn, Kung Lao and Kano are some fantastic honorable mentions.
His secondary fatality is my favorite. Johnny`s dialogue, along with the whole "And the Oscar goes to...!" was perfect, played wonderfully with his personality. I wish the other characters had some fatalities like that. And his second fatality was...violent. I mean, REALLY violent. And considering the subject matter (freakin' Mortal Kombat!) that is saying something. Not to mention I love the camp of how it subtly breaks the laws of physics, AND Im a sucker for fatalities where the winner holds their opponents head up in triumph!