I practise various songs in different tunings.
For standard-range tuning i play:
Slayer: Angel Of Death, South Of Heaven
Metallica: Battery, Seek And Destroy
Mayhem: Deathcrush
Opeth: To Bid You Farewell, Black Rose Immortal, April Ethereal
Atomizer: Hesitation Wounds
The Haunted - Bury Your Dead, Leech, Shadow World


For really drop tuned stuff i play:
Amon Amarth - Victorious March, Dragons Flight (what little i know - CORPSEVOMIT! get onto it mate ) lol
At the Gates - Cold, Slaughter Of The Soul, Blinded By Fear, Unto Others, The Swarm
Soilwork - The Chainheart Machine
The Berzerker - Disregard