Intro-Only Point of View

The opening of a story is told from Tom's point of view, about how he saw Jack and what Jack did, and then the point of view shifts to Jack, the actual protagonist. -- exclusively, or predominately.

This is a way to ease the audience into the story, because Jack is a very odd or outlandish character, and viewing him from the outside first makes the transition easier. It can cause problems if the opening doesn't arouse sufficient interest in Jack, and the audience may dislike the transition for that reason.

It can also be used to arouse interest in a crime by showing the victim's sufferings before we switch to the crime-solver.

The Sacrificial Lamb is frequently the introductory character. The Decoy Protagonist is, sometimes, if his part is told in his point of view.

Compare Framing Device, which can serve the same purpose, but has some character recount the story in retrospective.

Anime and Manga

 * Episode 20 of Code Geass: R2 opens with an inner monologue from Suzaku Kururugi.

Film

 * The opening sequence of Halloween is a single POV shot from the perspective of Michael Myers, building up to The Reveal that Michael is a small child.
 * The opening sequence of Peeping Tom is from the perspective of Mark's camera.
 * Sherlock Holmes: A Game of Shadows starts from Watson's narrative perspective before jumping into the Holmes-centric plot

Literature

 * In Dan Abnett's Warhammer 40000 novel Brothers of the Snake, the first undertaking is told not from the point of view of Priad, the Space Marine, but that of a woman on the planet to which he was summoned.
 * Harry Potter opens with the POV of Vernon Dursley as he goes to work and witnesses the wizarding world celebrating Harry's survival and Voldemort's defeat, followed by Dumbledore's meeting with McGonagall and Hagrid about Harry's future (the film version opens with the latter scene).
 * Goblet of Fire begins from the POV of Frank Bryce, a Muggle who accidentally eavesdrops on Voldemort, and becomes a Sacrificial Lamb in order to establish that Voldemort is at large again in Britain.
 * Half-Blood Prince begins from the POV of an unnamed Prime Minister, the recipient of an Info Dump that sums up the series thus far; it then goes on, more distantly, to follow Narcissa Malfoy and Bellatrix Lestrange as they interrogate Snape, who gives an account of his actions so as to support the idea that he has been working for Voldemort all along.
 * Deathly Hallows begins with a meeting of Voldemort and his Death Eaters, not from any specific POV, giving a general idea of what they are up to.
 * A Hero of Our Time by Mikhail Lermontov does this twice. Part one is told by the main character's old friend to The Watson, part two--by The Watson himself, and only the last three chapters are narrated by Pechorin (main character).
 * In Cryptid novel Discount Armageddon opens with the omniscient point of view to introduce the whole family watching Verity. After the prologue, the rest of the novel is first-person point of view from Verity.
 * Happens in the Mistborn books. Two-thirds of the prologue of the first book is in the POV of a random noblebman who gets killed offscreen between the second and last third of the prologue, and a peasant on said nobleman''s estate who shows up only once, very briefly, later in the book. The third book sort of uses it, the prologue is from the POV of a character that gets further point of view chapters later, but it's very short, and the beginning of the first chapter is from the point of view of the leader of a random settlement.
 * Each of the A Song of Ice and Fire books start this way. The opening POV character always dies by the end of their section.
 * The introduction of Willa Cather's My Antonia is told from the viewpoint of a character who meets an old friend, Jim Burden, and the two of them reminisce about their youth in Nebraska and their friendship with Antonia. The rest of the book is a first-person narrative from Jim.
 * In Robert E Howard's "The Devil in Iron", a fisherman goes into a ruin, takes up a knife, and dies. The rest of the story is how this collides with Conan the Barbarian.
 * In "Black Colossus", a thief breaks into a tomb, fights a great snake, and screams with horror with what he sees. Again, the rest of the story is how this collides with Conan the Barbarian.

Live Action TV

 * In their first episodes, both the old Doctor Who and the new focused on human characters -- Barbara and Ian, Rose -- who tracked down mysterious happenings and found the Doctor at the bottom of them.
 * An episode of House did this in the literal sense, for a patient with locked-in syndrome. The first fifteen minutes or so of the episode were shot through the patient's eyes, with his thoughts in voiceover.
 * This happens a lot on Bones (and probably other crime dramas as well). About one out of three episodes opens with some random characters living their lives, then finding the Victim of the Week. The POV then switches to the main characters for the rest of the show.

Visual Novel

 * In Fate Stay Night, the prequel chapter is told through the point of view of Tohsake Rin, instead of the protagonist Emiya Shirou. In the actual first chapter you see some of the events that took place in the prequel chapter from Shirou's point of view.

Web Comics

 * In Spare Keys For Strange Doors, the first story is told from the point of view of a woman who finds the two main characters to tell them about her friend's problematic use of magic, and the second from a ghost's.