Since actors sing in musicals, I excluded the genre to avoid the obvious. Here are some of the actors who sang in their movies that weren’t musicals. Some of them played singers and some of them were just doing it out of love. The numbering is random.

1) Heath Ledger – 10 Things I Hate About You

10 Things I Hate About You is a modern and successful romantic comedy that takes place in a high school and is remotely based on William Shakespeare’s Taming of The Shrew:

Here, the new kid at the school (Joseph Gordon Levitt) bribes the school’s most gossiped-after, rebel boy (Heath Ledger) to date his love’s sister. But when the rebel actually likes the girl and fails to get her attention, he does something dramatic: He serenades her with the help of the school band – broadcasted throughout the school. The song is “Can't Take My Eyes Off You.

2) Joseph Gordon Levitt- Zooey Deschanel- 500 Days of Summer

 500 Days of Summer

Tom Hansen (Joseph Gordon-Levitt) has fallen for his new co-worker Summer (Zooey Deschanel) big time. He does try the friendly approach as she comes along with him and his friend to a karaoke night. Both actors sing, separately.

3) Jennifer Aniston, David Schwimmer, Courteney Cox, Lisa Kudrow - Friends

Courteney Cox has a funny Karaoke incident when she finds out about what can be more embarrassing than a bad voice: The audience loves her and cheers her on. But despite the fact that she has sung well, the audience is just having a blast with the fact that spotlights are making her blouse transparent.

Lisa Kudrow plays Phoebe. She plays her guitar and sings awfully to the annoyance of other characters. Her song Smelly Cat is a Friends classic.

In one of the later seasons, Rachel (Jennifer Aniston) and Ross (David Schwimmer) have had a baby together. Ross has noticed that the baby only smiles when he is singing a dirty song. Rachel disapproves but soon gives in to her desire to see her baby smile. Imagine the rest of the  gang’s surprise when they see their two friends rapping about loving big butts in front of their newborn.

4) Kathleen Turner - Friends

Kathleen Turner played Chandler Bing’s (Matthew Perry)’s father (who is now a woman) for several episodes. This father has a glamorous job: He (she) has his own musical show every night.

5) Jonathan Rhys Meyers- August Rush

August Rush is the fairy tale-like story of an orphan trying to find his parents. Despite falling in love at first sight, Leila (Keri Russell)- a concert cellist and Louis (Jonathan Rhys Meyers) –singer and guitarist for a rock band- get separated because of Leila’s father. Having inherited his parents’ musical genes and more, the orphan tries to find them through music.

6) The Wedding Singer- Adam Sandler

The Wedding Singer is a 90s movie set in the 80s. Adam Sandler plays Robbie, a wedding singer. He meets and falls in love with a waitress (Drew Barrymore). But his own fiancée dumps him and Adam’s depressing singing creates hilarious moments, especially when he takes even the most energetic and upbeat hit of the era and turns it into a miserable experience.

7) I love you, Man – Paul Rudd and Jason Segel

Paul Rudd plays Peter who finds a best friend and best man in Sydney (Jason Segel). Their bond gets stronger by their mutual fascination with the rock band Rush. They perform their songs in Sydney’s garage.

8) Russell Brand, Jason Segel- Forgetting Sarah Marshall

Russell Brand plays the popular and obnoxious Aldous Snow, a rock singer. He is the annoying new boyfriend of Sarah Marshall (Kristen Bell)- the female actress her ex Peter (Jason Segel) is trying desperately to forget.

Jason Segel’s Peter is a composer and in the film, he begins working on a rock opera on Dracula. He sings parts throughout the movie.

9) Jack Black- School of Rock

Jack Black plays the loser singer of a rock band. When the band members can’t take his theatrics anymore, he gets kicked out. Shortly after, he finds himself as a substitute teacher for kids. And they are about to learn more about music than they ever bargained for.

Jack Black sings in real life as well. He has a comedy rock band called Tenacious D.

10) Val Kilmer- The Doors

Val Kilmer plays the lead singer of The Doors, Jim Morrison. While it is usual for actors to sing using their own voices for roles, Val does use his voice playing one of rock’s most controversial and talented frontmen. All the vocals are his, and this adds to the value of his performance.

11) Tom Cruise- Top Gun

Tom Cruise sings to Kelly McGillis in a bar, engaging his pilot friends into his duet. He sings You've Lost That Lovin' Feeling". He does get her attention.

12) Mel Gibson - Conspiracy Theory

The song plays towards the end of the video. Mel Gibson’s character Jerry Fletcher is an odd cab driver who happens to be madly in love with a beautiful lawyer named Alice (Julia Roberts). He is fascinated by her and he even watches her house as she works out. He mumbles the famous song “Can't Take My Eyes Off You".

Spoilers:

At the end of the movie, as he is driving in the car with federal agents, they all sing the song together.

13) Joaquin Phoenix- Walk the Line- he played Johnny Cash

Joaquin Phoenix played real life singer Johnny Cash in the movie.

14) Keanu Reeves- Sweet November

Keanu Reeves plays Nelson Moss, a cold, workaholic and not so sensitive advertising guy. After a pitch for a client goes bad, Nelson runs into a very pretty yet peculiar woman (Charlize Theron). For some reason, she is very interested in Nelson and not just for sex. As Nelson lets her change him so that he can enjoy life better, he falls for her. At one scene, Nelson prepares a very fun and miscellaneous gift package, including a dishwasher, dance tutorial and him singing to her at a night club.

15) Gerard Butler, Hillary Swank – P.S. I love you, Jeffrey Dean Morgan

In P.S. I Love You, Gerard Butler’s Gerry has met the love of his life Holly (Hillary Swank) in the most fun circumstances. The second time they see each other is at the bar Gerry is playing the guitar and singing with his band. The movie is not told in a chronological order as most of their scenes together are memories – Gerard Butler’s character dies almost immediately after the movie starts.

One of the flashbacks is to Gerard Butler rocking the classic Mustang Sally. He later tricks his then wife Holly to sing. She starts singing a song by Prince, quite well and sexily, until she trips over wires and has a horrible accident.

Another singing actor in the movie is Jeffrey Dean Morgan, who plays an Irish musician. I am not sure he uses his own voice singing, but he does really play the guitar.