There are the obscure ones like Dennis Christopher and the kid from Willy Wonka, but, per @mentioning_it_all, I gotta think deeper than that. 

I don’t know if it counts because the role isn’t over, but can you imagine Mariska Hargitay as anyone other than Olivia Benson? It’s a big hit, but it feels like one hit. 

Otherwise, Elijah Wood, John Stamos, Josh Holloway?

Gretchen Mol was supposed to be a 90s it girl, and that...never happened. 

Tbh only Rachel and Monica were popular to me after Friends 

Hayden Christensen and Rupert Grint come to mind! Franchises are.... impossible to escape from! 

We were all supposed to be excited by Rachel Lee Cooke after She's All That, but nothing really hit for her again. 

I like this question, because we aren't referring to a Jake Lloyd who just did one movie and ghosted. Instead, it's the actors who couldn't score a second hit, no matter how much they tried. 

-Jennifer Grey (her nose job ruined any hope she had)

-Taylor Lautner (if you combine Twilight into one)

-Hayden Christianson (though I loved Shattered Glass)

Inspired by a post made earlier about the worst movie made by an actor, I referred to Alicia Silverstone as a one hit wonder in film, and now I'm intrigued of other "one hit wonder" actors in either film or television. 

One Hit Wonder Actors