Vincent Price and Charles Bronson star in an aerial game of Battleship? I don't want to give away much, for those who haven't seen it, but the clash of those two mentioned stars is interesting enough. The film is actually watchable, riffable and not super common (yet still easy to find. I watched it on YouTube, the last time).
It's not a scary movie, hence why I waited until after Halloween to suggest it. I think it would be a good one to add to the Rifftrax library, like some of the other things I've suggested that you have since done.
Cheers!