I love most of the Skyclad covers. The best is probably:
And one great cover is actually the back of the "Songs from the wood" album by Jethro Tull:
And absolutely thrilling is the "Vitamin Enhanced Ozric Tentacles" 6-CD Box:
Veeerrrrryyyyyyyyy nice: BranVan3000's "Discosis":
Forgot about this one from some obscure scandinavian metal-outfit:
and finally, from the hilarious section: