Hal

HAL-9000 was an artificial intelligence from 2001: A Space Odyssey by Arthur C. Clarke. HAL was short for Heuristically programmed, ALgorithmic computer. Hal was part of the computer in the Discovery One spaceship. HAL began to malfunction, and when the astronauts decided to disconnect his cognitive circuits, HAL decided to kill them. In the sequel, 2010: Odyssey Two, HAL was restarted, and his previous attempt to kill the astronauts was revealed to be due to a conflict in his programming. HAL sacrificed himself to save the astronauts, but was turned into a non-corporeal being by the monolith.

Harold 'Hal' Jordan was one of several humans to become member of the Green Lantern Corps. He was a member of the U.S. Air Force. When Abin Sur, a member of the Greeen Lantern Corps, crash landed in California, the power ring chose Hal Joran as it's replacement officer. He was one of the founding members of the Justice League. 

Hal Yorke was a vampire in the U.K. television series Being Human. He was born in the late 15th century. He went on a bloody rampage for centuries, and gained such an evil reputation that even the Old Ones were afraid of him. In the 20th century he lived with a werewolf named Leo and a ghost named Pearl. After Leo died, Pearl went with him to the afterlife, leaving Hal with another werewolf and ghost, Tom and Annie.

Halfast 'Hal' Gamgee was a Hobbit and a cousin of Samwise Gamgee in the Lord of the Rings by J.R.R. Tolkien. 

Hal the Archer, and Hal Korwin where minor characters in the Doctor Who television series. 

Hal is typically a nickname for Harold or Henry. As a stand alone name it is not very popular. In 2011, only 15 boys were named Hal.