Human sacrifice

Human sacrifice was practiced in many ancient cultures. Victims were ritually killed in a manner that was supposed to please or appease gods or spirits. On very rare occasions human sacrifices still occur today.
Reasons for human sacrifice include:

• Sacrifice to accompany the dedication of a new building like a temple or bridge. Chinese legends hold that thousands of people were entombed in the Great Wall of China, though they were not.
• Sacrifice upon the death of a king, high priest or great leader; the sacrifices were to serve or accompany the deceased leader in the next life. Mongols, Scythians and various Mesoamerican chiefs could take most of their household, including servants and concubines, with them to the next world. This is sometimes called a "retainer sacrifice," as the leader's retainers would be sacrificed along with their master.
• Sacrifice for divination; a priest would try to predict the future from the body parts of a slain prisoner or slave. According to Strabo, Celts stabbed a victim with a sword and divined the future from his death spasms.
• Sacrifice in times of natural disaster. Droughts, earthquakes, volcanic eruptions, etc. were seen as a sign of anger or displeasure of gods and sacrifices were made to appease the divine ire. Cretans tried to stop the destruction of their island this way.
• Ritual combat: the victim was killed in a nominally fair fight against a warrior.

Human sacrifices were made in the Bronze Age Celtic religions in Europe, and in rituals related to worship of Norse gods (modern Ásatrú and Druidism do not condone such practices). However, because most of the information comes from outside sources (Greeks and Romans for Celts and medieval Christians for Norsemen) who may have had ulterior propaganda motives, contemporary historians consider them suspect.

Modern human sacrifice

Human sacrifice still happens in some traditional religions, for example in muti killings in eastern Africa. Human sacrifice is no longer officially condoned in any country, and such cases are regarded as murder.
Some people in India are adherents of a religion called Tantrism (not to be confused with Tantric Buddhism); most either use animal sacrifice or symbolic effigies, but a very small percent of them still engage in real human sacrifice:
Even groups of the richest and most powerful people in the world still gather for an annual mock human sacrifice of an effigy at the Bohemian Club in California.

After a rash of similar killings in the area -- according to an unofficial tally in the English-language Hindustan Times, there have been 25 human sacrifices in western Uttar Pradesh in the last six months alone -- police have cracked down against tantriks, jailing four and forcing scores of others to close their businesses and pull their ads from newspapers and television stations. The killings and the stern official response have focused renewed attention on tantrism, an amalgam of mystical practices that grew out of Hinduism. (In India, case links mysticism, murder - John Lancaster, Washington Post, 11/29/2003)

In Western cultures no human sacrifice occurs beyond murders committed by serial killers or the largely unsubstantiated rumors of Satanic ritual abuse. Modern occultists consider such sacrifices unnecessary, or use them only in the symbolic form where the volunteer "sacrifice" is not actually killed. Christianity holds that the crucifixion of Jesus was history's most important sacrifice.
Some people have tried to extend the use of sacrifice-related terminology. A few writers have written that war--so often charged with religious and nationalistic symbols--is a form of human sacrifice. Abortion, also a politically charged topic, has been called an act of human sacrifice to the god of convenience.
Modern muslim terrorist suicide bombers as well as Japanese kamikaze pilots can be claimed to be examples of human (self-)sacrifice too.
Historically prominent human sacrifices include:

• Lindow Man in the United Kingdom
• Tollund Man in Denmark (from the article: At first, Tollund Man was believed to be a rich man who had been ritually sacrificed, but recent analysis suggests that he may simply have been a criminal who was hanged and buried in the peat bog.)