What a fun question! Really made me go through my lineups because I wanted to know the answer myself
I located these examples:
Isabelle Adjani:
1975: Best Actress, The Story of Adele H.
1981: Best Actress, Possession
1983: Best Actress, One Deadly Summer
1988: Best Actress, Camille Claudel
Jennifer Jason Leigh:
1994: Best Supporting Actress, The Hudsucker Proxy
1995: Best Actress, Georgia
2015: Best Supporting Actress, The Hateful Eight
Billy Bob Thornton:
1996: Best Actor, Sling Blade
1998: Best Supporting Actor, A Simple Plan
2001: Best Actor, The Man Who Wasn't There
And a few two-timers which admittedly isn't as impressive but still:
Irène Jacob:
1991: Best Actress, The Double Life of Veronique
1994: Best Actress, Three Colors: Red
Michael Keaton:
1988: Best Supporting Actor, Beetlejuice
2014: Best Actor, Birdman
Jeremy Irons:
1981: Best Actor, The French Lieutenant's Woman
1988: Best Actor, Dead Ringers
Dennis Hopper:
1977: Best Supporting Actor, The American Friend
1986: Best Supporting Actor, Blue Velvet
Charles Boyer:
1944: Best Actor, Gaslight
1953: Best Actor, The Earrings of Madame de...
