There are a few that I can't stand, but here are two that stand out BIG off the top of my head.
1. Muskrat Love - America, Captain & Tenille (projectile barf!)
2. Lovin' You - Minnie Ripperton (when she hits that high note my blood pressure hits new highs)
Everyone share your list of worst songs. Note: I'm mostly focusing on rock, pop, Christian, alternative and country as I don't really listen to anything else.