The Ator movie that got the MST3K treatment was shown under the title
The Cave Dwellers. You should really check it out if you haven't seen it. It's one of their absolute best.
I love the scene where Ator tells the girl and his assistant, Thong (yes "Thong"), to sneak in while he distracts the guards. Ator disappears for about 2 minutes and suddenly swoops in on a hanglider, dropping grenades. I'm sure that Joel and the bots speak for everyone when they groan, "Oh, you've got to be kidding me!".
As for recommended B movies, I'm partial to Conquest, a stone age sword and sorcery flick directed by Lucio Fulci, best know for his horror pictures like The Beyond and Zombie.
It sort of combines Conan and Quest For Fire (an excellent film in its own right).
Lots of nudity, blood, brain eating, and monsters.
The downside is that every scene has fog in it. Every scene. Sometimes it made it hard to tell what was going on. I'm still not sure what attacked the heroes in the water (but reviews described them as zombies).
Also, as far as I know, it hasn't been on video in years.
And the first Deathstalker film is great, especially the boar man. Before LotR, he was the best example of an orc. In fact, he's so cool his scenes were inserted into every one of the Deathstalker sequels (which are all horrible, btw).
Of course, it goes without saying that The Sword & The Sorcerer is a classic. BTW, anyone own the dvd of this flick? I've heard that there are a lot of complaints about flaws in the disc (freezing up, I think).
Also, one of the premium channels remade a bunch of old horror movies from the '50's. I saw She-Creature and Earth VS The Spider and they were both excellent.
Spider starts off as kind of a take on Spider-Man and goes off into horror as the guy becomes more and more spider-like.
And She-Creature deals with a killer mermaid in the 1800's (I think that's when it's set). Very cool.
I've heard that two of the others in the series, How To Make A Monster and The Day The World Ended, are also great. In fact, the only bad film in the series is supposed to be Teenage Caveman, which is a shame since its the one I was most looking forward to. One critic likened it to when a person films his own vomit and calls it art. Not exactly a ringing endorsement.
And, while not a fantasy film, I really recommend Battlefield: Earth. One of the funniest films ever made. It's a shame that MST3K never had the chance to get their hands on it. My own favorite part of the film was when I realized that the lightbulb were still intact after 1,000 years.