Gary Oldman would be my go to overall. My sleeper pick would be John Goodman. For someone whose breakout role was a comedy sitcom, he has huge range and screen presence.
I think his role in Revenge of the Nerds came first.
I have five that I rate goats because even if the movie is total dogshit, its still worth watching because they are in it.
1) Gary Oldman - No question the all time GOAT as an actor with immense range.
2) Sam Rockwell- Arguile is the only movie that sucked so bad that he could not save it, even with Cavil helping him.
3) Edward James Olmos - Bill Fucking Adama is his peak, but a lot of his B work is incredible.
4) Tim Curry - The ultimate scene stealer.
5) Collin Farell - Dude will do anything and kill it every time.
Honorable mentions:
Christopher Walken - Done some amazing roles, but kind of descended into being a parody of himself.
Jeremy Irons- Made Die Hard 3 the best of the series and killed it in Margin Call despite being in less than 1/10th of it.
James MacAvoy- Probably the most fearless actor of the modern era, behind Rockwell. Filth, Split, Wanted, and on and on.
Vincent Denofrio- Glad he got recognition for Kingpin (only thing worth anything in Echo), but he has tons of different roles to his credit, beginning with Blood of Heroes.
Lance Henrickson and Andrew Robinson- The all time kings of B-List Acting with tons of credits on their resume.