The best covers you've ever heard ..

Sacred Reich - War Pigs
Overkill - Frankenstein
Nevermore - Sound of Silence - Silent Hedges/Double Dare
Some of the Metallica ones from Garage Days Re-revisited
That's all of the good ones I can think of.

I'd have to say about 80-90% of covers suck. I'd really be perfectly content to never have another cover on any CD I bought.
 
In Flames - Everything counts (Depeche Mode)
Sanctuary - White Rabbit (Jefferson Airplane)
Queensryche - Gonna get close to you (Lisa Dal Bello)
Tori Amos - Strange Little Girls (entire album)
Chris Caffery & John West - Run to the Hills (Iron Maiden)
Therion - Summernight City (ABBA) :D

And a lot more.... :)
 
Nevermore - Sound of Silence
Metallica - Astronomy (Blue Oyster Cult)
Hmmm... I never heard In Flames' cover of "Everything Counts"
Will have to grab it.
 
Sentenced did house of the rising sun? the Rolling Stones song?
SHIIIIT I GOTTA get that thing!
 
One of my personal favorites, though it's hard as hell to find is Iron Maiden covering Jethro Tull's "Cross-eyed Mary." Fucking excellent. Also, though it's uber-obscure, there's a cover of "Dream On" (originally by Aerosmith) with Ronnie James Dio on vocals and Yngwie "Sir Wanks-a-Lot" Malmsteen on guitar. Man, Dio ripped that song up.
 
Cradle of Filth - Hallowed be thy Name
Megadeth - Paranoid
Nevermore - Sound of Silence
Metallica - Breadfan
Sacred Reich - Sweet Leaf
Godsmack - Sweet Leaf
Black Label Society - Snowblind, No More Tears
Sentenced - Digging the Grave
Sepultura - Symptom of the Universe
....

and about 40 others...
 
SLAYER- INNA GADDA DE VEDA??!?!?!!?
Nevermore-Love Bites
Motorhead-Louie,Louie
Pantera-The badge
Sepultura-Orgasmatron
Anthrax-The Cowboy Song
Fear Factory-Cars
Megadeth-Mechanix, remixed,re-mastered version........I know it's not really a cover but it's a helluva lot better then "the four horseman"
 
Gee, [KOTNO]Narrot, you are right... The Seawinds is fantastic!!! But the original is very good, too, right?.... ;)

NoLordy, I don't think that The house of the rising sun was Rolling Stones. It was more The Animals, wasn't it? ;)
 
Pantera - "Planet Caravan"
In The Woods - "Epitaph"
Type O Negative - "Paranoid" :)

Oddly I don't like Nevermore's - "Sound Of Silence" that much, maybe because the original was so perfect....