A cameo is usually a brief appearance or voice part in a work of the performing arts. These roles are generally small and can either be appearances in a work in which they hold some special significance or renowned people making uncredited appearances. Most cameos are usually added for entertainment purposes or are a filmmaker's way to pull a witty prank on the audiences. Some, however, have had an integral status in the movies they are featured in, elevating them to a great extent. Here are five such cameos:

Roman Polanski in Chinatown (1974)
The short edgy man who slashes Nicholson's nose in Chinatown is none other than the director of the film, Roman Polanski. The scene involves a quick cut and the spray of blood covering Nicholson's face. It has been executed with such brilliance, given that no props were used. Plus, it wasn't rehearsed, which means Nicholson's anxiety was genuine.

Martin Scorsese in Taxi Driver (1976)
This is perhaps the most iconic cameo in the most iconic film ever. Scorsese conveys the unnerving tension associated with a premeditated crime flawlessly in the cab scene. His delivery could rattle anyone and one would easily dread the outcome of his actions.

Christopher Walken in Pulp Fiction (1994)
Walken's cameo lasts only four minutes, but it does leave a lasting impression. In the scene, Captain Koons (Walken) makes Butch aware of the places the watch (which Butch was possessive about), had to hide to survive the war. Walken changes his calm tone to a rather perky one, exaggerating the ridiculous situation which is perfectly capped by the kid's straight face.

Bill Murray in Zombieland (2009)
In the 2009 film, Zombieland, Bill Murray is clad in makeup so he won't be recognized as a human by zombies. He spends his days playing golf and re-enacting scenes from Ghostbusters in his mansion before being mistaken for a walker and shot accidentally. What ensues is a minute of dark comical mourning with a deadpan from Murray that is so good.

Alfred Hitchcock in every movie
Hitchcock has made cameos in almost all his films. He had the talent to blend two primary atmospheric horror techniques : the characters' presence and the viewers' presence. Alfred Hitchcock made his perspective the viewer's and also went to the length of being physically present. With every cameo, he draws the viewer to the scene and then makes him/her distracted to identify the mastermind. His lingering presence did not limit the horror to the screen. It landed up being all around us.