We all stumble across terrible movies when confined to aeroplanes or childhood sleepovers, but if you have seen more than 10% of these movies then you should be as ashamed as the people who made them!
[Edit May 2021 - Rating threshold reduced to 1.5. When I started this list the threshold was 2.0 and there were fewer than 120 qualifying films. This has now risen to more than 550. I assume we all want a warning about the worst of the worst and I hope this list still offers that service. Enjoy!]