First Name:
* Jack Black: Actor, comedian, and musician
* Jack Nicholson: Actor
* Jack White: Musician
* Jack Gleeson: Actor (known for playing Joffrey Baratheon in "Game of Thrones")
* Jack Harlow: Rapper
* Jack Ryan: Actor (son of actor Dennis Quaid)
Middle Name:
* Leonardo DiCaprio: Actor (full name: Leonardo Wilhelm DiCaprio)
* John Travolta: Actor (full name: John Travolta)
* Daniel Radcliffe: Actor (full name: Daniel Jacob Radcliffe)
* Michael Jackson: Singer (full name: Michael Joseph Jackson)
Last Name:
* Jackman, Hugh: Actor
* Blackjack, Jack: Professional poker player
* Black, Jack: Fictional character (the protagonist in the novel "The Adventures of Jack Black" by Robert Louis Stevenson)
Nicknames:
* Johnny Depp: Actor (real name: John Christopher Depp II, often goes by "Johnny")
* Jackie Chan: Actor (real name: Chan Kong-sang, but goes by "Jackie")
This is just a small sample, and there are many more celebrities with "Jack" in their name!