Standard Monoblack Zombie Deck.
Playing with this deck:
WHATEVER YOU DO, DO NOT PUT MORE THAN ONE HEARTLESS SUMMONING ON THE FIELD
This deck is very versatile and is built to control the board. There are two ways to play this deck--with a heartless on the board, aim to get the big baddies out and reduce early game damage as much as possible. If you cannot get a heartless out, play more conservatively as your creatures are resistant. Phyrexian Crusader is a much stronger card than it initally looks--double protection, and he can take on up to a 3/3 without dying; first strike+infect can be used to keep an opponent under control.
Either way, creature advantage will be yours later in the game. Use Dismembers early and try to save your Doom Blades for later. You have a lot of options with Phyrexian mana--more often than not, it'll be better to use life than actual mana. Your Wurmcoil Engine combined with a late game Lashwrithe will reap you loads of life. You can bring back Wurmcoils or Unbreathing Hordes (if you have Zombies out!) with Sheoldred if you have board control, or Solemns if you are looking for mana.
Remember that with the Phyrexian Crusaders, you have two different ways to win the game. If your opponent isn't careful and allows you to get one with a Deathmantle on him, GO FOR THE INFECT WIN. A Crusader with a Lashwrithe and Deathmantle on him is likely a game over. If you've switched from Zombies to Control, you'll also have swords; with just one sword, your opponents only chance is an blue source.
I've had people ask me why I included the Unbreathing Horde in a deck not built with a large amount of zombies. My reasoning is that they are a persistant creature; with a Cemetery Reaper out, they are indestructible due to their mechanic. They are resistant to damage removal, and forcing players to use destroy burn on what is one drop can frustrate people.
SIDEBOARD CONVERSATION
I'm still undecided weather or not to keep this a zombie major deck or not. I've included the options for change in the sideboard if you're finding that zombies aren't cutting it for you.
Swap out the Cemetery Reapers and Unbreathing Hordes for Perilous Myrs and Myr Superion. This will allow you slightly more board control. If you DO decide to change from zombies, I would swap the Ghoulcaller's Chant for a Geth, and also the Deathmantles for the swords.
EDITS 11/5/11
Edit#1:
After several FNM attempts with this deck, I've had more success with inserting the two swords from the sideboard and taking out two Unbreathing Hordes. This deck has placed first 3/4 weeks, with the second place finish to a R/U burn that was able to keep creatures off the board with unsummon/burn and casting from the graveyard with Burning Vengeance to do damage.
Edit #2
I removed the Call to the Grave from this sideboard and decided to throw in some Bloodgift Demons for draw. I haven't had this issue due to the Solemns draw when they die. REQUESTED EDIT
