I'm kinda an indie film type, so there's not many conventional classics on my list.
Girl, Interrupted
Se7en
Requiem for a Dream
Black Swan
The Virgin Suicides
American History X
Ex Machina
Donnie Darko
Stake Land
Sweeney Todd: The Demon Barber of Fleet Street
Zombieland
Birdman
12 Years A Slave
Bridesmaids
Celeste and Jesse Forever
TP to the OP for making me think about this list.