Terminator Salvation -- John Connor Dies, Is Replaced by a Cyborg
Terminator Salvation tells the story of cyborg kryptonite John Connor leading a war against an army of machinated overlords in a post-apocalyptic future. Partway through, he teams up with a guyborg named Marcus Wright, who used to be human until he was turned into a metal abomination by the nefarious robots, and he is having trouble adjusting. The two end up battling through a prison to rescue a bunch of captive Resistance fighters, but John is badly wounded and needs a new heart, because apparently furious murderbots can piston-fist you in the sternum without killing you instantly.
Knowing that the humans need John Connor in order to continue their fight, Marcus offers his own heart (one of the only parts of his anatomy that are still organic) up for transplant, heroically sacrificing himself so that the Resistance can live on.
"I should tell you my cholesterol is through the roof. I never could get enough chicken wings."
The Original Ending
John and Marcus invade the robo-prison to free their comrades, and once again, John gets horribly wounded. However, in this version, he has absolutely no chance of surviving, robot heart or no. Marcus has been badly damaged, too, and since he will need to be rebuilt, John's wife comes with up a solution: