Only folktales, emotional movies, and fictitious plays commonly display this level of heroism. Although life sacrifices do occur in reality, we do not always hear about the bravery of such deeds.
1. During WWII, American lieutenant John R. Fox noticed that his position had been taken by German forces. He sacrificed his own by ordering an artillery bombardment on his position. On the same day, the US Army launched a counter-offensive, and Fox’s body was discovered with 100 German troops.

On the 26th of December 1944, Fox found himself in a hopeless position in a home in the Italian town of Sommocolonia.
Fox was a member of the 92nd Infantry Division and the 598th Artillery Battalion’s front observer. His unit was stationed in the Italian city, but the Germans unexpectedly conquered it on Christmas Day.

The US forces were obliged to evacuate due to intense artillery assaults by the Nazis, but Fox was unable to do so. Fox didn’t think twice before ordering a counter-offensive by retreating US troops. He pushed them to fire again, even if it meant annihilating his observation party.
This deed resulted in the deaths of 100 Germans, delayed the Nazi offensive, and gave the soldiers time to regroup. Sommocolonia hamlet was afterwards recovered by the US. On May 15, 1982, Fox was posthumously awarded the Distinguished Service Cross.
On January 13, 1997, the medal was changed to a Medal of Honor. [Source]
2. Maximilian Kolbe, a Polish priest, was imprisoned in the Auschwitz Concentration Camp by the Nazis. Father Kolbe volunteered to take the place of a prisoner who was completely unfamiliar to him when the camp guards sentenced him to death in 1941. The lucky man lived for 94 years till 1995, surviving the concentration camp.

Kolbe was a missionary in Japan during the 1930s and the creator of Militia Immaculate, a worldwide evangelizing organization. In 1941, the Germans arrested him for helping Jews and imprisoned him in Warsaw.
The priest was then taken to Auschwitz, a concentration camp. Until July 1941, when a convict fled the jail, he was assigned degrading duties.
To deter the prisoners from trying additional escapes, the guards chose ten guys and condemned them to death by hunger. Franciszek Gajowniczek, one of the ten unfortunates, pleaded in vain for his wife and children.

Kolbe stepped forward and offered himself as a self-sacrificial replacement for Gajowniczek, which the deputy commander accepted.
For the commander, assassinating a 47-year-old Catholic priest was a decent offer.
The priest survived two weeks without food or water in the starving bunker before passing on August 14, 1941.

After the priest saved his life, Gajowniczek survived for another 54 years, dying in March 1995 at the age of 94. [Sources: 1, 2]
3. Liviu Librescu was a Holocaust survivor and Romanian-born Israeli and American scientist, engineer, lecturer, and teacher. During the 2007 Virginia Tech School massacre, he blocked his classroom door while the attacker fired through it. He gave his life in order to save 22 of his 23 students.

On the morning of April 16, 2007, Librescu and his pupils were in Norris Hall when the attackers arrived. Later that day, the kids described the events in detail. Sueng-Hui Cho, a 23-year-old shooter, opened fire while the professor was teaching mechanics.
Cho murdered a total of 31 individuals in this incident.
When the students heard gunfire, the professor just closed the room’s door because there was no way to secure it from the inside. Cho fired a semi-automatic handgun through the door, and the old professor was hit by every shot.

The 76-year-old professor heroically maintained his ground in order to gain time for his students to flee the window. Librescu was born in 1930 and, like millions of other European Jews at the time, he suffered greatly.
Despite this, he had a successful academic career, spending 20 years as a professor at Virginia Tech. [Sources: 1, 2]