When I was 17 on a late Friday night and I may or may not have been toking, my friends managed to convince me to watch X-Men: The Last Stand with them (the only conditions in which I can be convinced to watch a movie involving superheroes).
Even sto... ahem... tired out of my mind, I was able to determine that was probably the flat-out worst combination of poor writing, poor directing, and poor acting I have had the displeasure of witnessing in my 23 years.
I like to think I have discerning tastes in films, which is why I have to be dragged by friends to watch a movie I even have an inkling is going to be bad. Sure, I could have watched something that was monumentally bad like this "The Room" I keep hearing about, but I should thank my lucky stars that the ones close to me aren't that cruel enough to subject me to that