1. Ryan Gosling
Life Before Sparks: Former Disney Mouseketeer with lots of indie cred but little commercial love.
The Big Break: In The Notebook (2004), Gosling plays a hopelessly devoted blue-collar kid who charms a southern heiress by fearlessly hanging off a Ferris wheel and lying in the middle of the road. After returning from WWII and finding her engaged to a rich lawyer, he wins her back by restoring an abandoned house.
Postscript: Grossing more than $115 million worldwide, The Notebook became Sparks' most indelible film adaptation and opened the door for Gosling to secure his white-hot-star status in critical hits (Half Nelson, which earned him an Oscar nomination for Best Actor) and box-office successes (such as Drive and Crazy, Stupid, Love., which earned him a nomination for World's Best Abs). He became an Internet sensation with the "Hey Girl" and "Feminist Ryan Gosling" memes and was the subject of protests when People failed to name him Sexiest Man Alive.

2. Channing Tatum
Life Before Sparks: Exotic dancer turned male model turned actor, mostly known for Step Up and G.I. Joe.
The Big Break: He's a surfer and a soldier, torn between love and duty, in Dear John (2010), the third-highest-grossing Sparks-based film. After an extended deployment costs him his long-distance relationship, he sells his most prized possession (spoiler alert: It's a coin collection) to pay his ex-girlfriend's dying husband's medical bills. Not surprisingly, this impresses the new widow—fade to black.
Postscript: Dear John proved Tatum was more than a Ken doll with dance moves. People's Sexiest Man Alive (2012 edition) went on to deliver hits like 21 Jump Street and Magic Mike, as an actor and a producer.

3. Liam Hemsworth
Life Before Sparks: Played a paraplegic on the Australian daytime soap opera Neighbours, then moved to the States, where his character was written out of Sylvester Stallone's The Expendables.
The Big Break: In The Last Song (2010), he's a musical—and muscular—college student who woos Miley Cyrus' rebellious new-girl-in-town character by helping her defend turtle eggs from predators and then seals the deal by transferring schools to move across the country to be with her.
Postscript: The Last Song may have been Cyrus' movie, but Hemsworth came out of it surrounded by buzz, quickly landing coveted starring roles in the Hunger Games trilogy and in the upcoming big-budget Arabian Nights, opposite Anthony Hopkins.

4. Zac Efron
Life Before Sparks: Singing-and-dancing Disney stalwart and preteen idol, unable to shake the High School Musical stigma.
The Big Break: Plays an Iraq War vet who, with his trusty German shepherd, is on a mission to find the woman whose photo kept him alive in The Lucky One (2012). Once they meet, he defends her from an abusive ex, bonds with her son through music, and eventually saves him from drowning . . . after they've performed at the town church recital.
Postscript: With upcoming roles in serious fare like the JFK-assassination drama Parkland and the drug-smuggling action thriller Autobahn, he is finally starting to be seen as a grown-up actor.

5. Josh Duhamel
Life Before Sparks: Fergie's husband had gotten roles on screens big (Transformers) and small (Las Vegas) but had yet to carry a winning project on his own.
The Big Break: Kind-hearted widower and devoted father of two in love with a woman on the run in this year's Safe Haven. As he heals from heartbreak (with the requisite boat rides and beach trips), he helps her break free from her dangerous husband.
Postscript: It's too early to tell how big a bounce Duhamel will get, but he's already building momentum, with several major films coming out over the next year. If he plays his cards right, he could be the next Sparks-made success story.