What Are Some Of Your Favorite Casting Choices?

Sir Ian McKellen and Sir Christopher Lee as Gandalf and Saruman respectively (LOTR and the Hobbit). Sir Ian McKellen and Sir Patrick Stewart as Magneto and Professor X respectively in the X-men movies. Both Mark Hamill and Heath Ledger as the Joker(both embody the character to a degree where they are now permanently linked with the role. As for the X-men and Middle Earth actors, they all play well off the other actor in the movie and are quite believable as the characters that they play.

I think the casting only the show White Collar was perfection. Matt Bomer and Tim Dekay were friends in real life and that carried on screen to their characters Neal and Peter respectively.
And Willie Garson is phenomenal, and so is everyone else.

Ryan Reynolds as Deadpool, RDJ as Iron Man, Chris Evans as Cap, Jackie Earl Haley as Rorschach, Arnold as Terminator, Matt Ryan as Constantine, Pierce Brosnan as Dr. Fate, Ruffalo as Hulk, Tobey, Andrew, and Tom as Spider-Man, Mar Hamil as Joker, Kevin Conroy(RIP) as Batman, Chadwick a Boseman as black Panther, Oscar Issac as Moon Knight, Patrick Stewart and Macavoy as Professor X, Hugh Jackman as Logan, Jim Carrey as The Mask.