G.P.506 (2008 Korea)

An army investigator is put in charge of a soldier unit to find out what
happened at G.P. 506 (and to possibly cover it up), which saw the original
team brutally massacred by one of its own (well that's what it seems?)
and what this second team uncovers is something terrifyingly devastating.

It's an unusual, but immensely unpredictable military horror/mystery
story covering its bases in an interestingly progressive non-linear narrative.
(source)

Tokyo X Erotika: Shibireru kairaku

"Reality deconstructed to form a surrealistic matrix, filled
with eroticas anatomized in the point of view of death,
eternity and samsara." aka an attemp at arty crap.

Double Indemnity (1944)

 

An insurance rep lets himself be talked into a murder/insurance
fraud scheme that arouses an insurance investigator's suspicions. (IMDB)

Directed by
Billy Wilder

Starring
Fred MacMurray
Barbara Stanwyck
Edward G. Robinson

Added to the National Film Registry in 1992

Death Rides a Horse (1967)

Death Rides a Horse (aka Da uomo a uomo, or As Man to Man) is a 1967
spaghetti western directed by Giulio Petroni, written by Luciano
Vincenzoni, and starring Lee Van Cleef and John Phillip Law. Bill
Meceita, a boy whose family was murdered in front of him by a gang,
sets out 15 years later to exact revenge. On his journey, he finds
himself continually sparring and occasionally cooperating with Ryan,
a gunfighter on his own quest for vengeance, who knows more than he
says about Bill's tragedy.
source

H (2002 Korea)

aka
H Hypnosis
H: Murmur

A serial killer named Shin-Hyun gives himself up to police. He confesses to committing a series of particularly horrifying murders of exclusively female victims. He is imprisoned, awaiting the death sentence for his crimes. Yet the killings do not stop. They continue with all the same characteristics trademarks of the Shin-Hyun serial killings.