Having an A-Lister cameo in a movie can be the greatest gimmick weapon in a director's arsenal. If a cameo is used well in a comedy it can get one of the biggest laughs in the film, think of Chuck Norris' random and unexplained appearance at the end of Dodgeball as the judge who determines the fate of the competition.
Similarly when an actor with a history linked to the film makes a cameo it can provide an extra level of meta detail, such as Johnny Depp appearing as an undercover cop in 2012's 21 Jump Street, a franchise based on the TV series which made Depp a household name.
However, if done wrong a misplaced cameo can take an audience right out of a movie as they spend the rest of the film's runtime thinking "was that Ferris Bueller who just popped up in Manchester by the Sea?"
Sometimes having a big name actor appear in a quirky three minute scene actually ruins any world building the film had managed so far by taking the audience out of the scene and reminding them where they are: in a dark room watching a film.
10. Mike Myers - Inglourious Basterds
Inglourious Basterds is arguably Quentin Tarantino's magnum opus with not a single line of dialogue wasted, managing to create one of cinema's most compelling villains in Hans Landa and featuring some incredibly tense scenes.
Looking at some of Tarantino's earlier work, he has taken some incredible risks when casting his films. He famously met a lot of resistance when making Pulp Fiction after Michael Madsen was unavailable for the role of Vincent Vega and he decided to pursue John Travolta for the part instead.
The studio was reluctant to cast Travolta who prior to Pulp Fiction had starred in the box office bomb Look Who's Talking Now, which is one of the rare films to have a 0% rating on Rotten Tomatoes. While Travolta's casting was ultimately inspired the same cannot be said of the bold casting of Mike Myers, who had slowly faded out of Hollywood post-Love Guru, who played British officer Ed Fenech in Inglourious Basterds.
Myers is one of the most influential comedic actors of his generation but his exaggerated English accent had more than a whiff of Austin Powers about it, and is impossible to take seriously in this otherwise fairly grounded scene. The cartoonish performance is so tonally off compared to the rest of the film that this scene sticks out like a sore thumb, which says something in a film where Hitler is gruesomely machine gunned to death in the third act.