Cofagrigus is a very good bulky ghost, the only problem it faces is severe competition from eviolite Dusclops. Calm Mind does make it a pain to take down though.
Cofagrigus @ Leftovers
Nature: Bold (+Def, -Atk)
Evs: 252 HP / 252 Def / 4 SpD
~ Calm Mind
~ Shadow Ball
~ Hidden Power [Fighting]
Set is very simple, but works great. Calm Mind raises your special stats, and after a couple of boosts, Cofagrigus can take hit on both sides of the spectrum fantastically. Shadow Ball is for STAB, while Hidden Power Fighting offers flawless coverage. Rest, despite its drawbacks, is Cofagrigus' only form of recovery, and after a few Calm Minds, it can sleepwithout fear of being OHKO'd.
Yamask also has a use, and makes a great suicide Trick Roomer.
Yamask @ Focus Sash
Nature: Any speed lowering nature
Ivs: 0 Spe
~ Trick Room
~ Destiny Bond / Grudge
~ Memento / Power Share / Will-O-Wisp / Toxic / Mean Look / Haze / Curse
This has to be level one to work, and is best being used as a lead. Any attack will get you to one HP, allowing you to get off a Trick Room. If the opponent is trying to set up, Disable it so they have to attack. Since they have to attack, Destiny Bon lets you take them down with you. Grudge also works well, as it allows for you to completely deplete the PP of the move that knocked you out. The last slot is very much filler. Memento is if they switched on your Destiny, and will force them to switch next turn. Power Share allows you to significantly cut an opposing sweeper's attack stats to very low levels. Will-O-Wisp can be used if your Focus Sash is still intact to cripple physical attackers, while Toxic cripples walls. Mean Look can prevent switches, and after Disabling the opponent's set up moves, you'll almost garuntee a Destiny Bond. Haze gets rid of any boosts they acquired beforehand, while Curse will force a switch. For this to work, you NEED Rapid Spin and anti- Hail and Sandstorm support.