The Sha Ka Ree Entity impersonating the image of the Judeo-Christian God
This entity claimed to be God but was actually a malevolent noncorporeal being discovered by the Vulcan Sybok and the crew of the USS Enterprise-A in 2287. It was imprisoned on a planet located within the Great Barrier, at the centre of the galaxy, which was believed by Sybok to be Sha Ka Ree of Vulcan mythology.
In 2287, this being assumed the identities of several mythological figures including the God of Sha Ka Ree to lure Sybok and the Enterprise to its location so that the starship could free it from imprisonment. "God" asked for the ship to help him spread his "wisdom" with the universe. Though Sybok wants to oblige, James T. Kirk was suspicious of "God's" motives and asked why he would need a ship. In response, "God" shot lightning from his eyes at the Starfleet captain. Spock tried reinforcing Kirk's point only to be shot as well. "God" asks Leonard McCoy if he doubts him too; the Doctor responded he doubts powerful beings attacking others for pleasure. "God" then reveals he was a prisoner of the core and wanted to get out. He changes into a form mimicking Sybok, to mock the foolish Vulcan for his arrogance. Realizing his mistake, Sybok sacrificed his life by thrusting himself into the entity so that the Enterprise and her crew could escape. Kirk orders a photon torpedo to be fired, killing Sybok but not "God". Angry, he proceeded to kill the remaining three. Kirk had Spock and McCoy beam away, leaving him to the mercy of the entity. The entity was apparently destroyed by the Klingons. (Star Trek V: The Final Frontier)
Background
The Human image portrayed by the "God of Sha Ka Ree" from Star Trek V was portrayed by actor George Murdock. The image of the Andorian god, as well as the other two unidentified gods (shown below), were among the images proposed to represent the "many faces of God" in Star Trek V. These images, however, did not make it into the final production of the movie, but were included in the Special Features section of the Star Trek V: The Final Frontier (Special Edition) DVD.
Apocrypha
According to the non-canon Q Continuum series of novels by Greg Cox, the Sha Ka Ree entity was known as "The One," and was exiled to the center of the galaxy for causing a civil war centered around the premature destruction of the legendary Tkon Empire millennia before being rediscovered by Picard and the crew of the Enterprise-D. He was an associate and contemporary of 0 (pronounced "Zero", as in nothing), the Beta XII-A entity, or (*) as 0 referred to it (used in type because its real name was apparently unpronounceable, or even incomprehensible, by Humans), and Gorgan in this endeavor.
The One was referred to by 0 as the entity "who created Monotheism." He was not originally of this plane and was summoned to this universe via the Guardian of Forever. After causing chaos among the Tkon Empire, he was subsequently defeated and his body destroyed by the combined efforts of Q2, female Q, and the Q who became known as Quinn; only his head remained, and that was subsequently sealed away by the Q Continuum at the center of the galaxy until his repentence or the heat death of the universe — whichever came first — while 0 was sealed outside the galaxy by the galactic barrier for all eternity.