Alas, Leslie Nielsen will always have been Frank Drebin (unless he's the Airplane doctor), and William Jackson Harper will always be Chidi Anagonye (this did deflate quite a bit of Midsommar's tension).
Of course, Eli Wallach can't cease to be Tuco Benedicto Pacífico Juan María Ramírez, Gian Maria Volonte the Indio, Rod Steiger Juan Miranda, Claudia Cardinale Jill and James Woods Max whereas at least Van Cleef oscillates between Mortimer and Sentenza.
Dominic West is stuck as McNulty, just like Walton Goggins is forever Shane. Actually, Matthew Rhys and Keri Russel will stay Jennings for a while. I'm slowly managing to detach David Tennant from The Doctor (not quite there yet).
Peter Dinklage is above all Living in Oblivion's Tito (despite The Station Agent). Geena Davis is The Long Kiss Goodnight's Samantha Caine even more than Thelma. Susan Sarandon is a witch from Eastwick more than Louise. Jeff Goldblum is a brundlefly above all. Both Elisabeth McGovern and Jennifer Connelly stay Deborah, and both Mel Gibson and Tom Hardy are Rockatansky (without the mask, I suppose Hardy would have been Bane instead).
Elliot Gould is Marlowe. Jonathan Pryce is Sam Lowry. Jeremy Irons is Elliot Mantle. Sam Shepard is Chuck Yeager. Ron Perlman is One. Jeremy Irons is Beverly Mantle. Ingrid Bergman is mostly Ilsa Lund, Walther Matthau is the Captain Red, Ferdy Mayne is Von Krolock even in Where Eagles Dare, Johnny Depp is so Corso, and Harvey Keitel stays the Wolf. David Niven is The Brain. McGoohan is of course forever 6 and/or Drake (the same thing in my headcanon even if not in his). Rickman is Alexander Dane (and probably lives it as Dane lives being Lazarus), and also my most geeky apologies to sir Alec Guiness because, well, you know.
As I haven't yet watched that Tony Hillerman adaptation, Wes Study is the guy from Mystery Men (Ben Stiller too, in fact). Piper Perabo is the girl from Lost and Delirious. Michael Madsen is the dude from Reservoir Dogs. Naomi Watts is the girl from Mulholland Drive. Nicolas Cage is the dude from Kiss of the Vampire. Angelina Jolie is the (well one) girl from Girl Interrupted, and so is Clea DuVall actually. Jon Voight is the dude from Runaway Train despite Deliverance. Peter O'Toole is The Stunt Man's Eli Cross despite Lawrence of Arabia. Christopher Walken is Max Zorin despite Deer Hunter. Mickey Rourke is Harry Angel despite Year of the Dragon. Scott Glenn is Mancuso despite the Keep. Guy Pearce is Ed Exley despite Ravenous. Carlyle is the creepy supporter from Cracker despite Ravenous. Jeffrey Jones is the Guy from Ravenous despite Beetlejuice. Also Steven Segal is solely the guy being hilariously flushed out in Executive Action. As for JCVD, well, he's JCVD.