There's a good amount of Enslaved that is in C#.
Venom - "Resurrection" is in C#
Most Bloodbath is in some form of A tuning, be it dropped (ala Nile) or straight.
Candlemass "Nightfall" and "King Of The Grey Islands" is definitely in C#
There are some At The Gates demos in C#...they even covered "Captor Of Sin" (Slayer) in C#
Dragonlord is C#
Behemoth are using either C# or half step down on 7 strings...have been using this since "Zos Kia Kultus"
Newer Mayhem
Machine Head pretty much uses a drop tuning on every album...it was some semi-tone pitch down a whole step and dropped for the first album, and has been 1.5 steps and dropped after that (drop-B, or whatever the fuck).
Torinojaws: Good call on Sabbath...the original, mofuckas! "Master Of Reality" is almost all C#.