Worst. Lyrics. Ever.

To this list, I submit:

Jessica Simpson: "I don't know what's come over me, but I think I know what it is"

Choclair: "If she's wid it"
"You know I'm wid it"
"I'ma hit it"

and the ever-beloved Sisqo: "She had dumps like a truck, truck, truck
Guys like what, what, what
Baby move your butt, butt, butt
I think I'll sing it again
She had..."

EDIT: Steve Schaming accurately points out that I've overlooked Lil' Jon with this gem:
"To the window (TO THE WINDOW), to the wall, (TO THE WALL)
To the sweat drop down my balls (MY BALLS)"

That particular song also contains gems like... Oh hell, the whole thing is tremendously terrible, just click here if you dare.