We've always skipped Sounds Dangerous, and WW to be a M...I can't really say they are the worst though, they just seemed boring.
The worst ones I've been on were the Circle of Life (put me to sleep), the second Imagination ride (no Figment), followed by the third Imagination ride (a pale reminder of the orginal, which was great). The original ride and post ride were fun! It was all about using your imagination, but now it's just lame. I love Eric Idle, but the images of him on that ride with all that make-up are just scary.
You'd think Imagineers would be able to make an attraction about inspiring one's creativity....