Mono black infect. But why?
When I first came across possibility to win just for ten poison counters dealt to an opponent, Deck with the key word "Infect" looked like something that needed to be done. Also, I don't like pay to much for hurting people, even though I like it and therefore the price is around $12.
So here's the brew:
Creatures, now with infect! Ichorclaw Myr starring as early blocker or a doom-bringer after little tweak, Phyrexian Vatmother in a role of main beater, Plague Myr in case of need a little ramp, Plague Stinger because flying is definitely useful and Hand of the Praetors for obvious reason of free poison counter and +1/+1 for all my bad boys.
Control in a form of Harsh Scrutiny and Distress
Cleaning the way for little big fellas with Bile Blight (if there are some aggressive tokens in bigger numbers) and Victim of Night for most possible treats.
Card draw? Aphotic Wisps and Sign in Blood
Evasion Aphotic Wisps again! Such wow, just for one . And Gruesome Deformity because let's do it next turn again.
The evasion goes very well with Virulent Swipe, round after round after.. ok, so maybe only 2 times but that is 4 poison counters on your shirt, again just for one
This deck might have some problem with black decks, though. This is where the Sideboard comes to play. Literally. Dark Betrayal and Nighthaze will let the evil shadows disappear ind the shadows.. You know what I mean.