Plague Marines
Okay, how i'm going to put this: You take a Chaos Space Marine, mix it with Nurgle, there! You have a Plague Marine, which is pretty much a walking sack of bile, disease and rot, just as Nurgle would want!
Seriously, Plague Marines are tough bastards, not just because their guys with Power Armor, their guys with Power Armor who have a body that can take HUGE amounts of damage before dying, and if they die, that'll still make Nurgle happy, for there will be a body to rot (But he'll be sad to see a servant of Nurgle to die)
Plague Marines usually armed with a Bolter, that is in very low condition, thanks to the fact that it has been decaying for a pretty long time, and Plague Marines are too busy not dying in their diseased are corrupted bodies, that they won't start fixing them that much. They can also arm them self's with a Combat Blade, that can unleash Nurgle's Rot on it's victims.
Most Plague Marines are in King of McDonalds Legion, the Death Guard, and serve their lazy boss in his Plague World, where they drink tea, and do truthfully nothing.