Heavy, thick, gloopy mud; can't beat (or puncture!) Maxxis Ignitor 1.9's. They only do tubeless in 2.1 tho, which I haven't tried, but they are just seriously good spring/autumn/mild winter tyres.
Useless on tarmac & slow on gravel tho, and slip on wet roots, but awesome in mud.
General 'winter' tyre (to be honest, I don't change them per season with British summers) I tend to use Schwalbe Nobby Nics on the rear which give good grip.
I have found too, where frame clearance permits, that mahoosive Geax Lobo Mas Loco 2.5's F&R are like pedalling a motocrosser about.
Silly lean angles, mud paddling ability, cushioning air volume and rock-pushing/bramble crushing abilities. Huge grins, but won't fit every bike, or perhaps everyone's sense of fun.
Amazing tyres tho, used them on a rigid bike and a full sus, and just never stop grinning (like an idiot) in all seasons..