Salems lot.ABSOLUTE MUST!
You need to own
Audition
Old Boy
May
Near dark
Irreversible
Versus
The story of Ricky
Kill list
Tattoo
Tale of two sisters
sympathy for Mr vengeance
The Orphanage
Funny Games
Braindead
Bad taste
The descent
Undead
Jacobs ladder
Dog soldiers
From dusk till dawn
Dawn of the dead
Opera
suspiria....ok ill stop now!

depends on the type of horror you want

1974 texas chainsaw masscre
poltergiest
amityville horror
the omen
the exorcist and exorcist 3 (skip the second unless you buy the boxset)
wolf creek (not classic but a good watch)
carrie
christine
the blob
re-animator
puppet master
childs play

could go on forever

Asylum
Dr Phibes
Vault of horror
Dr terrors house of horror
Torture garden
Ginger snaps
willard
Hellraiser
The beast must die
toolbox murders
The woman
The gray man
Ichi the killer
Frontiers
Martyrs
Aye,depends on what youre after really..I havent even started on zombies yet!!

Some British horror not mentioned yet:

Mum and Dad
The Living And The Dead
The Children
Heartless
Salvage
House On Straw Hill
Xtro
28 Days Later
28 Weeks Later
Eden Lake
Dog Soldiers
The Descent
The Last Horror Movie

I havent gone into my dining room yet!! they are all there!

last house on the left (original and remake)
i spit on your grave (original and remake)
house of 1000 corpses
devils rejects
hills have eyes (original 1 & 2 and both remakes)
the mist
children of the corn (1 to 3)
dead silence
when a stranger calls
the hitcher (original and remake)
vacancy
the strangers (one of my favourites of the last 5/10 years)
bay of blood
beyond
house by the cemetery
the orphanage

Trying to mention a few that havent already been said:

Jaws
Cronos
The Devil's Backbone
Hellraiser II
Braindead
The Sentinel
The Fog
Martin
Eraserhead
Anything that includes the effects of Ray Harryhausen or Rob Bottin
Carnival of Souls
The Changeling
The Devils
Demons
Nosferatu


I'm pretty sure we could all add a couple hundred to our lists too....

1. Night of the Living Dead - original. Tom Savini's remake was decent.
2. Dawn of the Dead - original. Greatest movie of all time. Refake is garbage.
3. Day of the Dead - original. Refake worse than garbage.
4. Hellraiser
5. Hellbound: Hellraiser II
6. Hellraiser III: Hell on Earth
7. Evil Dead
8. Devils Rejects
9. Cannibal Holocaust
10. Brain Dead - also known as Dead Alive.

Ten must see films for any horror fan!

i dont think all these movies are essential.especially not movies like christine and the decent

Christine is a great film dude. Do you not like it? I reckon all the older Carpenter films are essential stuff the guy didn't put a foot wrong back then.