This isnt necessarily my fave horrors, but just thought I'd try and think of different ones.

A, An American Werewolf in London
B, Braindead
C, Children Of The Corn
D, Day Of The Dead
E, Evil Dead
F, Freddie v Jason
G, Ghoulies
H, House On Haunted Hill
I, Island Of Death
J, Jeepers Creepers 2
K, Killer Clowns From Outer Space
L. Last House On The Left
M, Maniac
N, Nightmare On Elm Street
O, Omen 2
P, Psycho
Q, Q The Winged Demon
R, Return Of The Living Dead
S, Saw
T, The People Under The Stairs
U, Urban Legends
V, Vamp
W, Wolf Creek
X, Xtro
Y, Young Frankenstine
Z, Zombie Flesh Eaters 2

I cheated a little bit with some of the sequels lol