Actors / Actresses you think of as one trick ponies, even if it's a good trick.

Dwayne Johnson
Vin Diesel

They both mostly do likable tough guy types and very well

I'm surprised nobody mentioned Arnold Schwarzenegger. A living, breathing action figure.

Kristanna Loken (one film: Terminator 3)

Hugh Grant (Only stars in rom-coms)

Jackie Chan (only stars in comedic martial arts movies)

Chris Tucker

Christian Slater. Slater is always Jack.
Jack Black, always the same over the top forced antics.
Will Smith, always the wise guy.
Tom Hanks
Kristen Stewart

Jason Statham

Jack Nicholson is like Jimmy Stewart, someone who always seems to be the same person, but who has such a huge range that their performances are always good. They aren't the kind of chameleon actors who seem to be completely different people in each role, yet they are different people. Actors like Nicholson and Stewart can be hilarious in one role, batshit crazy in the next, mellow and good-natured in the one after that, romantic and lovable after that, etc. There's a high level of skill involved, an actor doesn't have to be a chameleon to be damn good.

That said, The Rock is the ultimate one-trick pony, even though I like the trick. He's always fun.

Jason Statham turned this into a nice career.

You know exactly what you're getting when you see one of his movies. I guess you can say this about most action stars. Arnie, Sly Stallone, JCVD..

Morgan Freeman and Bruce Willis also come to mind.

betty white lol that funny slut