Wow, you really want that HUGE list?
Since I'm a tribute albums collector, I have heard so much crap. Especially in the early Dwell records tribute, mostly death/black bands butchering all they touch (like the Rush tribute).
Some songs I really disliked the cover (no offense to anyone, this is my belief):
Nevermore - 'Love Bites' (Judas Priest)
U.D.O - 'Metal Gods' (Judas Priest)
Death - 'Painkiller' (Judas Priest)
Slayer - 'Dissident Aggressor' (Judas Priest)
Cradle Of Filth - 'Hallowed Be Thy Name' (Iron Maiden)
Six Feet Under - 'Wrathchild' (Iron Maiden)
Eric Zimmermann - 'Man On The Silver Mountain' (Rainbow)
Gardenian - 'Gotta Give It Up' (Thin Lizzy)
Blood Coven - 'The Temples Of Syrinx' (Rush)
Cydonia - 'Save Us' (Helloween)
Anal Cunt - 'Killing Yourself To Live' (Black Sabbath)
Brutal Truth - 'Lord Of This World' (Black Sabbath)
Pitch Shifter - 'N.I.B.' (Black Sabbath)
System Of A Down - 'Snowblind' (Black Sabbath)
I have lots more to rant, but these are a clear example