Ichthyoallyeinotoxic Sliver 
Creature -- Sliver Fish
All slivers have Poissonous 1 (Whenever a creature with poissonous deals combat damage to a player, that player gets a blowfish counter. A player with ten or more blowfish counters hallucinates wildly, has a terrible stench, undergoes wild convulsions, and can't take any actions for the rest of the game.)
http://en.wikipedia.org/wiki/Ichthyoallyeinotoxism
EDIT: It's a fish joke. Poisson means 'fish' in French. :)
Posted By:
Salient
(1/3/2013 10:34:07 AM)
No amount of life can stop ten poisonous counters from causing loss.
Posted By:
Karthwine
(11/24/2009 4:17:44 PM)
this guys extreme potential kind of got overshadowed by Scars of Mirrodin with infect. 5/3 Trample haste that deals damage as poison counters for 5 mana.. yeah, you sac it at end of turn, but who cares?
Posted By:
PolskiSuzeren
(9/23/2010 3:19:30 AM)
A poison player might run or sideboard Leeches, just in case their opponent neutralises the poisonous creatures. Target takes damage equal to the number of removed poison tokens, that can be enough to kill.
Snake Cult Initiation is another great back-up card for if your opponent removes the Virulents, or just use it as a finisher.
Posted By:
A3Kitsune
(1/25/2010 8:14:26 PM)
Infect sliver is infectious.
Posted By:
ClockworkSwordfish
(4/23/2011 9:00:31 PM)
This card made me want to make a sliver deck. It's THAT GOOD.
Mandatory combo sliver: Shadow Sliver
Blue/Green/White sliver deck, here I come!
Posted By:
Snaxme
(12/4/2009 3:40:54 PM)
Its poison is pretty terrible (most of the time you'd rather just use a muscle sliver and kill them with damage.) But it only costs one mana, which is important -- slivers have few one-mana drops, and they benefit a lot from getting something out on the first turn (because as situational as its ability is, it still benefits from all your later slivers, too.)
Remember, one huge problem with this is that your opponent can just shut down your poison plan by killing your virulent slivers -- and even if they're at 9 poison counters, doing so will immediately make all those counters meaningless.
Posted By:
Aquillion
(3/23/2013 1:32:18 PM)
funny card :D I use it myself personally
Posted By:
Zeeek88
(1/21/2010 11:11:05 PM)
2 of these guys, Shifting Sliver and 2 other random slivers secure a one hit K.O.
Posted By:
zeyette
(4/16/2010 8:20:24 PM)
We definitely need an infect sliver, along with an Eldrazi sliver that grants annhilator 1 to all creatures...but I suppose they would be just a little broken
Posted By:
Superllama12
(8/11/2011 8:42:58 PM)