I love to play as black and also as blue.
Right now I have a really effective deck in black, that has a lot of instants that destroy creatures, and exile them. I also have the Toxrill, the corrosive slug that brings each creature down by -1/-1 each turn. As well as four Westgate Regent Vampires, that multiple in damage each time they hit the player. Basically, I keep the opponent at bay by eliminating their creatures before they even leave summoning sickness, and I bide my time to bring out the big guns. It has proven pretty effective, but some people have decks that really blow it out of the water.
I also made a modified version of it that has a lot of spells that force the player to discard, or allows me to choose which card to discard. It is really annoy I am sure to be on the receiving end of because I get rage quits from time to time, right out the box.