Mull of Kintyre wins by a big loch for me, if I never heard that dirgy song again it would be too soon. For some obscure reason it gets quite a bit of airplay around this time of the year.
Far too many songs by Queen, or those long, drawn out 'ooh-listen-to-me-I-can-sing-cos-I-can-hold-a-caterwauling-note-for-more-than-five-seconds' monstrosities. e.g. Celine Dion or Whitney Houston. Pick one.
Far too many to name: virtually anything by Queen; all those female warblers that TLO mentioned
But there are five absolutely stand-out ones for me:
Free Bird by Lynard Skynard
Power of Love by Jennifer Rush (I think)
Vienna by Ultravox
Pina Colada Song by Rupert Holmes
and the worst of all, 10cc's Dreadlock Holiday
Those are the five records I would confine to the deepest, darkest reaches of hell.
Required by law to be played at every single wedding reception EVER, usually by a DJ called Rik, thereby causing every person over forty in the marquee to drop their cheese & pineapple sticks and drunkenly get their groove on, shouting out "oooh, now this is what I call music!".