The Ordinary Boys - I Love You.
Isn't it just the most horrific piece of music ever? From the awful lyrics, to the fact his stupid voice can't handle the big long notes, all topped off by an irritating trying-too-hard-to-be-smiley-pop-music tune. It's a special shame because 9 to 5 and Boys Will Be Boys were pretty good pop songs, really.
Anyway, the song supersedes Christina Aguilera - Dirty as my new least favourite song of all time. Well done to it.
Honorary mentions in this category also go to Gwen Stefani - Wind It Up and Robbie Williams - Tripping.