Paura Nella Città dei Morti Viventi (1980) (Italy)
City of the Living Dead Fear in the City of the Living Dead The Fear The Gates of Hell Twilight of the Dead
You will probably find this film either really good or only mediocre, depending on the kind of zombie film you like. Directed by Lucio Fulci, it's about how the suicide of a priest sets the way for the gates of hell to open, and how four people discover this and try to stop it. It's got some of the goriest scenes you will likely ever see in a zombie film.
Personally, I saw it as more of a mediocre film. The acting and editing are not great, but you have to accept that in a lot of zombie films. The movie consisted of long stretches of tedium interrupted by scenes of intense gore. The gore scenes were well done, and if that's what you're looking for, then look no further. The plot, although slow and drawn out, holds the movie together well enough.
There are some plot points that are either confusing or unbelievable. For instance, the town pervert, Bob, who is being blamed for the killings, is running around town and hiding, trying to escape the spirit of the suicidal priest. He chooses to hide in the garage of the man whose daughter he once attempted to molest. This leads to an unpleasant end for Bob, and not from the zombies. Let's just say that there happens to be a lathe in the garage. The motivations for some of the other characters are just as unclear in other parts of the movie.
This movie was also known as The Gates of Hell and City of the Living Dead.