Blood Freak (1972)

How bad is it? It's astoundingly bad.
Should you see it? Yes. It's mostly dull, but you won't forget it.

The most memorable thing about this film is the on-screen narrator, who sits in a poorly panelled room, chain smoking, as he extols on the dangers of pollution. Then he has a coughing fit! It goes on for a while and they didn't re-shoot, so you start wondering if it's intentional.

A Bible-thumping girl and her partying friends get tied up with scientists (one with a comb-over for the ages) and a poultry ranch and marijuana that's been contaminated. It leads to one of them becoming a rampaging- get this - turkey monster! It's just a rooster head being worn by a guy, who then attacks. It's surprisingly bloody.

Added: There's currently some speculation that this film is intentionally bad. I think not.