I instinctively avoid bad movies, its like a 6th sense. But here are a couple memorable stinkers:
Intersection (remake)
The Keep
Magnolia
And this one I am adding for my wife, I personally loved the movie but when I finally talked her into watching it, as the end credits began to roll she actually said "Are you joking? Thats it? I kept waiting on something to happen and now its OVER?!?!??!":
The Big Kahuna.
Those other 3 I listed, I was actually saddened that I lost that time spent watching those and could never get it back. I mourned my lost time