Black/Red Lifesteal (Standard)

This deck's strategy is simple: prevent your opponents from gaining life (burn spells and Erebos, God of the Dead), steal their life (Sanguine Bond, Soul Feast, Polluted Bonds, Bloodhunter Bat, etc.), and of course, WIN by reducing their life total to 0. The defense of this deck revolves around enchantments and a few creatures. Mogis, God of Slaughter (which is very cheap to get out!) forces your opponent to either take two damage or sacrifice a creature. Now, since they are already taking a lot of damage, they will probably want to sacrifice a creature, leaving the field empty for you to attack (although it isn't really needed too often in this deck). Also, Sheoldred, Whispering One has the ability to return creatures from your graveyard to play during your turn, and also, force the opponent to sacrifice a creature during their turn.
Now for the fun part:
There are three primary win conditions in this deck (assuming that they are still alive by the time you get these cards out).

1) Master of Cruelties: Force your opponent to sacrifice creatures with Mogis, God of Slaughter and Sheoldred, Whispering One and then attack them ONLY with Master of Cruelties. If Master of Cruelties is not blocked, the opponents life total is reduced to 1. Simply use Lightning Bolt or another burn spell to finish them off. Master of Cruelties is a 1/4 deathtouch, first strike, so if by any chance he does become blocked, at least you kill a creature.

2) Bloodchief Ascension and Mindcrank: Bloodchief ascension gains a "quest counter" during each end step if an opponent lost two or more life this turn. When it has 3 or more quest counters, when a card is put into an opponents graveyard from anywhere you may have them lose two life and you gain two life. Mindcrank says that when an opponent loses life they also mill themselves that many cards. Basically, Bloodchief ascension deals them two damage and Mindcrank mills them two cards, making an endless cycle of death and life gain.

3) Sanguine Bond and Exquisite Blood: Another infinite lifesteal combo that wins you the game in the same turn (again, just use a small burn spell on any opponent and they will all die). Just read the two cards... It's actually quite funny how well these two enchantments work together. The Bloodchief Ascension/Mindcrank combo is perfect for 1v1 (as well as this combo). However, in a multiplayer game, the Sanguine Bond and Exquisite Blood combo is much more suitable, as it will kill each opponent in the same turn.