Woo hoo! I'm doing Hooptober for the first time to motivate myself to watch some of the movies on my main Halloween list, and also to branch out a little bit and stretch my horror comfort zone.

10 Anniversary Films:
Abbott and Costello Meet Frankenstein (70th)
Halloween (40th)
Halloween H20: 20 Years Later (uh... another 20 years later)
John Carpenter's Vampires (20th)
Bride of Chucky (20th)
Invasion of the Body Snatchers (40th)
Attack of the Killer Tomatoes (40th)
Killer Klowns From Outer Space (30th)
Cloverfield (10th)
The Lair of the White Worm (30th)

Six decades (turned out to be nine):
Every decade from the 1920s to the 2010s except the '30s. (I'll have to get some more Universal monsters into next year's challenge.)

Six from before 1970 (also turned out to be nine):
The Cabinet of Dr. Caligari (1920)
Abbott and Costello Meet Frankenstein (1948)
Creature From the Black Lagoon (1954)
The Curse of Frankenstein (1957)
Horror of Dracula (1958)
Eyes Without a Face (1960)
The Birds (1963)
Kwaidan (1964)
Night of the Living Dead (1968)

Six countries:
Kwaidan (Japan)
Mr. Vampire (Hong Kong)
Suspiria (Italy)
Eyes Without a Face (France)
The Cabinet of Dr. Caligari and Nosferatu: The Vampyre (Germany)
Lair of the White Worm (UK)

Six movies by some combination of George Romero, David Cronenberg, Clive Barker, Terence Fisher, Sergio Martino, and Bill Lustig:

Romero:
Night of the Living Dead
Dawn of the Dead
Day of the Dead

Cronenberg:
Scanners

Fisher:
The Curse of Frankenstein
Horror of Dracula

Two films about flying things that kill you:
The Birds
Q

One silent movie:
The Cabinet of Dr. Caligari

One aquatic menace:
Creature From the Black Lagoon

Two films by female directors:
Near Dark (Kathryn Bigelow)
A Girl Walks Home Alone at Night (Ana Lily Amirpour)

One living inanimate object:
Child's Play

One with Barbara Crampton:
Re-Animator

And, of course, two by Tobe Hooper:
The Texas Chain Saw Massacre
Poltergeist

Plus maybe these two for extra credit:
Tales From the Hood
Tales From the Hood 2

EDIT, September 2020:
Okay, so I only managed to watch 21 of my picks during the 2018 Hooptober season. Since then, however, I've watched or rewatched another four from this list, completed the 2019 challenge, and made a solid start on the 2020 edition.