The reigning king of grip whatever the weather is doing, Maxxis High Roller still rules if you're looking for a totally surefooted, sturdy and inexpensive tyre.
The steeply ramped centre tread means you're almost looking at two different tyres in one, as in-line grip and rolling speed are dramatically different depending which way round they are.
Have them running for maximum scoop effect though, and they'll power paddle through most mire, with the soft compound rubber gluing them to any rocks or roots.
There's a bit of a lurch over to the side knobs, but once you're there they're equally tenacious in nailing off-camber or cornering grip. They rarely clog too, and they shrug off damage even at low pressures making them an outstandingly grippy tyre in mixed conditions.
They are very slow rolling in the Sticky Compound version though, so go for the only slightly less tenacious 60 duro Maxxpro versions if you value velocity. Low prices mean fast wear isn't an issue though.