Jake Lloyd (aka Anakin Skywalker) moans and bitches to his dad Arnold Schwarzenegger about how he needs a Turboman doll for Christmas. After 89 minutes of beating up Santas, blowing up policemen and dealing with a neurotic fast talking Sinbad, Arnie finaly gets his hands on the doll. Little Anakin shows his appreciation by immediately giving it to Sinbad. His reason for this was, he "has the real Turboman at home". I however doubt Arnie can run at all, let alone at turbo speeds. His lat muscles are too big. Bad move padawan.
Jack Dawson - His warmth
Perhaps the most unnecessary sacrifice ever.
I know Jack and Rose were in love (I mean they spat off a boat and had steamy car sex), but I don't think there was any reason for him to freeze himself. The floating door thing was easily big enough for two. The only explanation I can think of is this, the pair of them took on Billy Zane and won, therefor Jack got cocky and thought he could take on anything, including hypothermia... Goodbye Jack.
Montgomery Wick - Bill Paxton
Scott Glenn climbs K2 as hard man with missing toes Montgomery Wick (with lines like "Up there, you're not dying, you're dead" he should've been called Mongomery Witt). Anyway, old Monty holds Bill Paxton responsible for his wifes death and basically goes on a massive revenge trip. In the final act, he's attached to a rope with Paxton dangling below him. With no hesitation he cuts the rope dropping them both to their deaths...I'm not sure if this is self-sacrifice or murder, but I think Wick should've yelled "THIS IS FOR PREDATOR 2!!!" as they fell.
Harry Stamper - His life
There's no easier way to obtain a one-way ticket to heaven then by sacrificing yourself to save everybody on Earth, and Ben Affleck of course. Harry Stamper saves humanity by blowing up a massive asteroid, but not before letting some Asian countries take a few hits first. He was probably thinking "thats for Pearl Harbor" (but if that were the case, he'd probably let Affleck die too).