I have a real soft spot for Savage Weekend and Eaten Alive (the Hooper one, hence my avatar). Also recommend House by the Cemetery, Devil's Nightmare and Cat in the Brain. If you want to discover some good obscure ones, as well as some total crap, I recommend getting those 50 BLANK movies box sets, particularly 50 Drive in Classics and 50 Horror Classics. Pure Terror is also a pretty good one, but feels like less effort went into it than the others. They're good because they simultaneously present you with plenty of material and encourage digging. Digging is good for your brain.

I'd recommend:

City Of The Living Dead
Inferno
Lair Of The White Worm
Session 9
Dagon
The Psychic aka Seven Notes In Black
The Perfume Of The Lady In Black
Society
Calvaire
Shutter
The Beyond
Curtains
Nightmares In A Damaged Brain
Brain Damage
Street Trash
Castle Freak
From Beyond
The Burning
Pieces
Visiting Hours

Crawlspace

The dead hate the living
American Gothic
In The Mouth Of Madness
Dracula 2000
Dr. Giggles
Milo

I like the American Godzilla movie. Now this film have nothing to do with Godzilla and I think the reason why it is unpopular is that people expected to get Godzilla just with Hollywood budget special effects and if that is what you are expecting then the movie is disappointing. However if all you are expecting is a decent giant monster movie and put the whole idea of Godzilla out of your mind then the movie is good.

Case 39. This is a typical scary little girl movie. There is nothing new in this film what so ever, however the film itself is rather ok and has a good story.

Queen of the Damned. This film is unpopular because it differs from the books allot. However if you look at it as a stand alone film, which is what it was made as then you might get allot of enjoyment of of this vampire flick.