There are bad actors and there are good actors. Then there are artists who redefine the art of acting.
One such artist is Gary Oldman. His range is astonishing and extra-ordinary.

9  times out of 10, I don't even realize that it's him acting the role  until I watch the credits.
 He has a scary knack of immersing himself  into roles to the point where it's difficult to separate the actor and  the character. I might even go onto say that this talent of his works against him when it comes to getting fame as people do not rate him on the same scale as Brad Pitt, Tom Cruise and George Clooney.

Anyway, here's a small sample of various roles:

Commissioner Gordon
The Nolan Batman Franchise


- A serious support role in a stellar superhero franchise.

George Smiley
Tinker-Tailor-Soldier-Spy

- Lead character in a recently-released spy thriller. 

Drexl Spivey
True Romance

-  Hard to describe if you haven't seen True Romance (and if you haven't,  you should!). A drug dealer and pimp from I think Caribbean origins.  Highly original.

Norman Stansfield
Léon - The Professional

- The primary antagonist to Jean Reno as hitman. Explosive, violent, cruel.

Ivan Korshunov
Air Force One

- Russian bad guy.

Jean-Baptiste Emmanuel Zorg
The Fifth Element

- As original as it gets (credit to Luc Besson). Industrialist and weapons manufacturer bent on destroying sacred stones.

Sirius Black
The Harry Potter Series

- A dramatic and noble role in a big franchise.

Rosencrantz (my personal favorite!)
Rosencrantz and Guildenstern are Dead

-  One of the title characters in the film version of a famous absurdist  play. A not-so-simple simpleton who ends up often accidentally  philosophical.