The "best-worst" one I can think of in recent memory was
Be Kind Rewind.
I generally dislike Jack Black's movies because I find him irritating. It was on HBO or something some lazy afternoon a month or so ago. It was pretty dumb, as expected.
But even though I wanted to really hate it, I found it somewhat amusing. There was some charm to it. I believe it stems from having worked in a little tiny video store during high school, and having a group of crazy friends that might actually have tried to 'remake' movies as they did.
I've also always sort of thought that
Mars Attacks! was a classic example of a best "worst" movie. Of course, it was done just like those classic B (C?) grade sci-fi moves from the 50's, so that was sort of what it was supposed to be. Always enjoy that one for its wonderful-awfulness ;).