In the underappreciated category:
Margin Call. Movie about the 2008 financial crisis. Just a bunch of people talking, but really good writing and acting. Amazing cast with Kevin Spacey, Paul Bettany, Jeremy Irons, Demi Moore, Stanley Tucci, etc. I think they all did it pro bono because the budget was $3.5M. The film only grossed $19.5M. It's on Amazon Prime now. Go watch it.
Thank You for Smoking. Tobacco lobbyist with an identity crisis. Only grossed $39M worldwide. Jason Reitman wrote this and Up in the Air. Solid comedy. Another awesome cast with Aaron Eckhart, Sam Elliott, Ron Lowe, Katie Holmes, Maria Bello, William H Macy, Robert Duvall and JK Simmons. Sometimes I wonder if the cast does this for free after they read the script.
Up in the Air. George Clooney flying around the country laying people off and having an identity crisis. Vera Farmiga (dat ass), Jason Bateman, Anna Kendrick, Sam Elliott, Danny McBride, Zach Galiwishhisnamewaseasiertopronounce and JK Simmons.
JK Simmons should be in everything.