I think the concept is flawed from the beginning.    Jerry Della Famina (marketing guru) once asked "what is the worst tv commercial" He than stated "wrong, the worst commercial is the one you don't remember"    I think the same is true of bad songs.   The truly bad songs are the ones you don't remember.

That being said, here are some truly awful songs I wish I didn't remember.

Kung Fu Fighting (did people actually buy that record?)
Seasons int he Sun
Billy don't be a hero
Yummy yummy yummy
Sugar Sugar
The legend of Billy Jack (one tin soldier)
My ding a ling
Knock 3 Times
Honey
Your having my baby

I have to stop- this is just to painful