Ok nobody has even replied so I'm gonna list some of mine, maybe it will start a discussion :)

The Texas Chainsaw Massacre (1974 - USA)
My favourite movie of all time. To me this is the perfect horror flick, I could go on for 10 pages with my reasons but I won't. I just know that I wouldn't change a frame of this movie and I think it's everything an American horror film should be - great sense of claustrophobia, the violence is mainly implied but realistic and focuses on the pain of the victims rather than the bloodshed, the performances are the best I have seen in a horror film and nobody in the film even seems like an actor, and it is one of the seminal films of the early '70s that changed the face of cinema by bringing horror & violence into the contemporary American backyard instead of the 1800s or castles or dungeons or mad scientists or monsters. The remake sucked balls and turned into I Know What You Did Last Summer by the 2nd half...

Maniac (1980 - USA)
Classic psycho-slasher flick, very underrated. Gritty & claustrophobic from start to finish with a Scorcese-esque urban New York atmosphere and violent murders against women. Joe Spinell's performance is amazing and he creates one of the screen's most creepy villains I think, the score is great, Tom Savini's special makeup effects are some of his best and the ending is awesome!

I Spit On Your Grave (1978 - USA)
The defining "rape-revenge" film which I don't think has ever been matched. This movie has probably the longest and most realistic & relentless depiction of rape ever put into a movie. Almost half the film is Camille Keaton being repeatedly chased and gang raped. There is no music in the entire film except for digetic sound when one of the rapists plays a harmonica, and one scene where she puts a record on to drown out the screams of a guy she has castrated in the bathtub, which makes for a super-realistic almost documentary style feel from start to finish that's ugly to watch. Hardly an enjoyable film but one that does perfect justice to the subject it's tackling. No way should this have been banned (after being available uncut for almost 20 years, they banned it in 1997 for excessive sexual violence) and I'm glad the OFLC overturned that decision last year to finally make it available again...

Bloodsucking Freaks (1976 - USA)
A campy low budget comedy-horror, but probably the best of it's kind. Just an unredeemably offensive orgy of nudity & violence from start to finish, with a quirky black comedy tone which lightens it, but at the same time the film is still pretty sick and I know alot of people who find it a bit disturbing. It's one of the only comedy-horror movies I know that can still have that kind of effect while also being hilarious. Like I Spit On Your Grave, this film was rated R uncut for 20 years and then the rising censorship in the late 90s saw the film get banned in 2000 for the first time. The ban was lifted this year again though and rated R again.

Last House on the Left (1972 - USA)
Wes Craven's debut film. This was one of the most important films of the 1970s to completely change what the horror movie was all about. Really, it was the first notable American horror film to have no zombies, no cannibals, no mad scientists or diseases, no monsters, or not be a period piece set in the Jack The Ripper days or a castle, etc. It was just 2 innocent young girls being beaten, raped, humiliated, tortured and killed by a bunch of thugs by a lake, then their parents getting a violent regenge, all presented (like I Spit On Your Grave) in a raw, bleak and realistic way. It's not perfect though, the comical interludes and music score have to go and take away from the brutality of the violence in some scenes. The 1975 Italian rip-off Night Train Murders is a much better (and far more underrated) film overall, but not as realistic as this, and you can't deny the importance & influence this film had in driving a stake through the heart of the hippy era and bringing abuot the golden era of the horror film! This one was banned here since it was made, until last year the uncut print was finally awarded an R rating and the movie was screened for the first time ever in Australia at Federation Square at a '70s horror festival - I was there!

Suspiria (1977 - Italy)
I'm a huge Dario Argento fan, this is visually his best work but not necessarily my overall favourite, I really can't decide because they all have strong & weak points. The weak points in this one are the script and the acting, but Argento's creativity is on overdrive in this movie as he creates the most nightmarish atmosphere I think anybody has. From the time the main character walks out of the airport into the pouring rain, accompanied by the chilling score from Goblin, and arrives at her ballet school where possibly the most intense murder scene ever in a film is taking place, Argento traps you in his nightmare where his lack of plot & structure don't matter anymore - after all, when do nightmares ever make sense?

Tenebrae (1982 - Italy)
An underrated "giallo" film (Italian mystery/slasher) by Argento. Same routine as most of his films - another amazing score by Goblin, stunning cinematography & inventive camera movements, great mystery, every murder scene is a memorable setpiece, a bevy of Italian babes being slashed up, and this one's ending is one of the best bloodbath's I have seen.

Ilsa, She Wolf of the SS (1974 - Canada)
If you're looking for something that will shock or offend people, you can't go past this notoriously banned exploitation classic. One of the most sadistic, violent & depraved movies ever made, this is one movie whose ban here I don't ever see being lifted, as it's sexual violence is way outside of the guidelines of a R rating. Filmed in secret on the set of Hogan's Heroes, don't expect anything like the sitcom! Apparently, the producer told director Don Edmonds (who hated the script he was given) to make something "groundbreaking", so Don decided to make something more extreme than anybody had ever seen on film before. So Ilsa, She Wolf of the SS came out so chocked full of sadistic torture scenes and depraved sexual violence, topped off with bleak & depressing surroundings of gangreen-ridden prisoners with skin falling off and offensive imagery such as blood-soaked naked corpses hanging upside-down from flag poles waving the swastika, that the producer actually ended up having his name taken off the film! It spawned a whole subgenre of "nazisploitation" and women's prison movies in the 70s, most of which were banned like this one though, or at least had to be heavily cut to get an R rating. The Ilsa sequels were nowhere near as sadistic.

Night Train Murders (1975 - Italy)
Italian rip-off of Last House on The Left. In fact, the American theatrical release of this (heavily cut) even got titled Last Stop on the Night Train! This is a better film overall though with a great music score by Ennio Morricone, beautiful cinematography, no silly comical interludes, and director Aldo Lado creates a great sense of claustrophobia on the train. However, while the rape & torture scenes feature some more extreme activities (an elderly peeping tom rapes one girl while the other loses her virginity to a knife), it's not as bleak and realistic as Last House on the Left.

The New York Ripper (1982 - Italy)
My favourite Lucio Fulci movie. Another Italian "giallo" film, but one of the nastiest. In this one, a quacking killer with a Donald Duck voice stalks the seedy red-light district of New York hacking up sexually active women. Apparently Fulci hated women coz he got screwed over so many times and got a kick out of his female characters being violated in his movies, and he goes to town in this one, with a nice selection of breast stabbings, nipple slashings, broken bottles up you-know-where and guttings from the crotch to the chest. Obviously the strict sexual violence guidelines saw this movie get banned here.

Basket Case (1982 - USA)
So underrated. A great black comedy, a great horror film, and a great urban violent New York thriller all at the same time. You actually feel for the separated twins (and the ending is quite emotional!), the black comedy is sharp and darkly humourous all the way through, the director keeps the story captivating until the end, and it has an awesome gritty New York vibe similar to films such as Taxi Driver and Death Wish.

Hollywood Chainsaw Hookers (1988 - USA)
My favourite whacky comedy horror. This one stays hilarious all the way through (not just a one-joke movie), has razor-sharp dialogue and film noir style voice overs, some off the wall & hilarious chainsaw killing scenes, steady dose of nudity (Linnea Quigley is a babe!) and a bizarre chainsaw ritual! It even stars Gunnar Hansen, the original Leatherface, as the leader of the chainsaw worshipping cult of prostitutes!

Cannibal Man (1972 - Italy)
Pretty much unknown film, I have this as part of a "Drive-In Double" DVD from the States with the banned Italian cannibal epic Mountain of the Cannibal God. I bought it for Mountain, but that was disappointing and this unknown little film that came with it blew me away! It's very Hitchcock in style, similar to films such as Rear Window, Rope and even the black comedy The Trouble With Harry where he deals with very few characters & locations, and turns one tiny simple idea into a masterpiece of suspense and puts the viewer right into that small world the film is set in. Mix that with a very French style of film making (particularly the characters who are really interesting & intriguing), and '70s Italian horror violence and you have Cannibal Man, about a decent hard working man who works in a meat factory and accidentally kills a taxi driver. When his girlfriend wants to go to the police he freaks out and kills her, and from there starts a chain reaction of murders in his house to try to keep his secret safe, but as the amount of missing people he knows and number of dogs sniffing around the smell coming from his house grows, he has to find a way to dispose of the bodies, and working at a meat factory he has just the way to do it!

Wow I've written alot, that will do... here are some other favourites:

Deep Red (1975) - Another "giallo" from Dario Argento
Phenomena (1984) - Argento again, another great film
Pieces (1983) - Badly made Spanish slasher but with some of the best murder scenes & ending!
Demons (1985) - Lamberto Bava's zombie flick which kills Romero's ones in my opinion!
Eaten Alive (1976) - Tobe Hooper's 2nd film, another claustrophobic rural American nightmare!
The Burning (1981) - Friday The 13th rip-off starring George Costanza!
The Texas Chainsaw Massacre 2 (1986) - Hilarious sequel, but they should've let Hooper edit it!
Reanimator (1985) - Inventive story, classic 80s horror
I Drink Your Blood (1970) - Seminal 70s grindhouse horror classic, Satanic hippies with rabies!
A Nightmare on Elm Street (1984) - Wes Craven's most creative movie
Halloween (1978) - The original American teen slasher flick, and the most suspenseful ever
The Hitcher (1986) - Not really horror but an edge of your seat highway thriller, awesome film!
Trick or Treat (1986) - The best "heavy metal horror" film there is
Psycho Cop Returns (1993) - Van Hell lent me this awesome comedy/horror about a killer cop!
Return of the Living Dead (1985) - The best zombie comedy-horror!