The Big Cube (1969)

If the motivations were strong enough, major studios might become involved (with explotation films), as in Warner Bros. 1969 anti-LSD, anti-counterculture film The Big Cube.(source)

The Big Cube is a 1969 Warner Bros. thriller directed by Tito Davison and starring Lana Turner, Karin Mossberg (in her first and only role), George Chakiris, Dan O'Herlihy and Richard Egan; it was one of Lana Turner's last movies. It is notable for its aggressive portrayal of LSD use and the 1960s youth counterculture as vicious evils. (source)

The Abominable Snowman (1957)

aka
The Abominable Snowman of the Himalayas

 

A kindly English botanist and a gruff American
scientist lead an expedition to the Himalayas
in search of the legendary Yeti.  

 

Mama's Dirty Girls (1974)

Mama loves men, but she loves money even more.
She's trained her three teenager daughters to
meet, marry and murder men for their money.
But soon the meet Harold and he got other plans. 

(IMDB)

Satan's Children (1975)

Unhappy and discontent suburban teen Bobby lives in abject misery in
the Florida suburbs. He's relentlessly browbeaten by his overbearing
stepfather and equally nasty shamelessly flirtatious tease of an older
step sister. Fed up with all this abuse, Bobby runs away from home and
winds up being savagely sodomized by a gang of greasy guys. They leave
Bobby clad solely in his underwear on the side of the road. Luckily
for Bobby he's saved by a nearby Satanic cult.
Attractive lady cult member Sherry gets the hots for Bobby, but cult
leader Simon thinks Bobby is too much of a weak, passive wimp to cut
it as a worthy member of the cult. So Bobby escapes from the cult's
dangerous clutches and exacts a harsh revenge on his stepfather,
step sister and the foul goons who brutally raped him in order to
prove he's got the right tough stuff to qualify as a soldier in
Lucifer's army.

"Satan's Children" is a sensationally sick, twisted and depraved doozy
of a low-budget 70's drive-in horror flick.

(source)

William S. Burroughs: A Man Within (2010)

The Exiles (1961)

Kent Mackenzie, USC Filmmaker, follows one 24 hr day of a native american couple and their friends in downtown Los Angeles, CA on & near Bunker Hill. With flashbacks to reservation life, the pathos of the "non-BIA approved" urban Indian life of poverty and utter hopelessness will move you beyond mere words. Homer & Yvonne are expecting a child - he is distant and lost, she abjectly passive and accepting of her fate. Absolutely real and so personal you may cry, knowing that nothing is going to get any better, and wishing that you could reach across time to make it different.
muputony 

Added to the National Film Registry in 2009 

Les Démoniaques aka Curse of the Living Dead (1974 France)

aka
Curse of the Living Dead

At the end of the last century on the north European coasts, lived men who feared
neither God nor the law. They lured ships towards the rocks where they were smashed
to pieces. These men then plundered the wrecks. They were called wreckers.  They
brutally rape two young woman and the woman re-emerge after making a pact with the
devil to get their revenge.
(source)

Baby Face (1933)

Although the Production Code had not been enforced in 1933, the studios still had local censor boards to contend with. One of the most powerful was that of New York, who took one look at Baby Face and rejected it in its entirety. With Joe Breen’s assistance, Warners cut and partially reshot the movie, using out-takes to get out of Stanwyck’s unavailability. Gone were the references to Nietzche (“use men to get the things you want!”), gone was a scene where a lecherous speakeasy customer gropes Lily’s breasts before she clonks him over the head with a bottle, gone was the scene where Lily and former maid Chico (Theresa Harris) get a free ride in a box car by means of Lily’s offering sexual favours to a guard. In was a new, explicitly moralistic ending. Even this modified form, Baby Face was too much for the prudish, and along with Convention City and The Story of Temple Drake was one of the first films to be withdrawn from American cinemas the following year. (By contrast, all three were passed by the BBFC, albeit with cuts of an unknown extent.)

In 2004, Library of Congress curator Mike Mashon was requested to strike a new print for showing at the London Festival. To his surprise, Mashon discovered a duplicate negative of Baby Face that was several minutes longer than the existing one. And so the pre-release version of Baby Face was rediscovered. (The uncensored version remained lost until 2004, when it resurfaced at a Library of Congress film vault in Dayton, Ohio. George Willeman is credited with the discovery.)

Source thedigitalfix

Added to the National Film Registry in 2005