Tier 1 - Potential pack one, pick one:
1. Liturgy of Blood
2. Mark of the Vampire
I wanted desperately to put Mark of the Vampire first, but when thinking about the actual decision, there's just no way I'd take Mark over Liturgy if the choice was in front of me. That said, Mark of the Vampire is essentially half a bomb, so I have no problem taking it first if there isn't a true bomb in the pack.
Tier 2 - Potential pick one in pack two or three, after my colors are established:
3. Deathgaze Cockatrice
4. Quag Sickness
5. Accursed Spirit
6. Blood Bairn
7. Child of Night
Deathgaze Cockatrice shows how absurdly good Vampire Nighthawk is; Deathgaze costs one more mana, has one less toughness, and doesn't have lifelink. And it's still a good card. Quag Sickness is a pretty solid piece of removal. Accursed Spirit is the black version of Bladetusk Boar, which was a nice card. Blood Bairn is a functional reprint of Vampire Aristocrat; it's still good. Child of Night, despite only having one toughness, can get a lot of work done.
Tier 3 - Solid cards to fill out the color:
8. Altar's Reap
9. Corpse Hauler
10. Dark Favor
11. Wring Flesh
12. Nightwing Shade
13. Festering Newt
Altar's Reap is one of those cards that really fits into black flavor-wise, and at instant speed, gives a lot of opportunities for extra value. Corpse Hauler is another example of how 2 power makes any two-drop fairly useful. As with most enchantments, I like Dark Favor more than most, but 3 extra power can turn any creature into a real problem. Wring Flesh is more of a combat trick than true removal, but a pretty good one. On a scale of shades, Nightwing Shade feels pretty close to the bottom. That said, it's still a 2/2 flyer with some ability to pump, so it's got value. Festering Newt will often be Festering Goblin, which makes it pretty decent in my book.
Tier 4 - Not exciting, but playable cards in color:
14. Mind Rot
16. Undead Minotaur
Mind Rot is one of those cards you never want to play, but you also hate seeing your opponent cast. Duress serves a specific purpose, and has a place in every sideboard. Nobody's going to call Undead Minotaur a beast, but it'll get plenty of work done. Shrivel is like infinitely worse than Cower in Fear...which often ended up as no more than a sideboard card.
Tier 5 - Cards I have a hard time seeing myself play:
18. Vile Rebirth
19. Minotaur Abomination
20. Shadowborn Apostle
Vile Rebirth isn't the worst...but it's pretty close. Minotaur Abomination is blah. If you have no finishers, it can squeak in, but if it's your best finisher, you're probably going to lose. Shadowborn Apostle is utterly worthless in limited.