Mila Kunis did not appear in the movie "Piranha." The film you might be referring to is "Piranha 3D," released in 2010. In "Piranha 3D," the actress who played a notable role was Kelly Brook, among others. If you have questions about Mila Kunis's other films or roles, feel free to ask!

The best "Piranha" movie is often considered to be "Piranha 3D" (2010), directed by Alexandre Aja. This film is praised for its blend of horror and humor, as well as its self-aware, campy style. It features a strong ensemble cast, including Elizabeth Shue and Jerry O'Connell, and is known for its over-the-top gore and entertaining premise of prehistoric piranhas wreaking havoc during spring break. While the original "Piranha" (1978) is a classic in its own right, "Piranha 3D" effectively revitalized the franchise for modern audiences.

While opinions on the scariest horror movie of all time vary, many critics and audiences often cite "The Exorcist" (1973) as a top contender. Directed by William Friedkin, it tells the story of a young girl possessed by a demonic force and the desperate attempts of her mother and two priests to save her. Its unsettling themes, groundbreaking special effects, and chilling atmosphere contribute to its reputation as one of the most terrifying films ever made. However, preferences for horror can be highly subjective, with films like "Psycho" and "Halloween" also frequently mentioned.

The 1978 film "Piranha," directed by Joe Dante, is rated R primarily due to its graphic violence and horror elements. The movie features scenes of piranhas attacking and devouring unsuspecting victims, which include depictions of blood and gore. Additionally, it contains some mild sexual content and language that contribute to its R rating. The film is known for its campy style and has become a cult classic in the horror genre, but its intense scenes and mature themes make it unsuitable for younger audiences.