"Im pretty open minded as far as music goes..."
There's a difference between open-mindedness and not know what is shit music.
Anyway, my list would be too long but I think anyone who doesn't sing live, without studio aiding, without "backing" tape or singers, should not be allowed the term "Singer" attached to them.
Oh and Britney Spears.
-AC
Many of the artists mentioned already and this one just came to mind:
Lumidee
Also a good number of girl/boy/coed 'band' members - usually one or two possibly three can actually song and the rest are just there for who knows what other then taking shares of the pay check their colleagues really earned more of.