gonna try once more to steer this back to small tires. spent some time this week on some new ones:
panaracer rampage SC 2.35 - this has their sticky rubber. mine is 710 grams. volume is between maxxis (old-school) 2.35 and kenda 2.35. rolls faster yet is far stickier than kenda sticky rubber. traction on north van roots/rocks is impressive, possibly even magical. best 1/2 pound i've added to my little bike. highly recommended. i don't care how fast it wears, they are pretty cheap.
michelin wild grip'r 2.1 - mine is 610 grams, rolls real quick, volume similar to maxxis 2.35 (very large for 2.1). medium-height wide-spaced knobs bite well into loam and muck, but firm-ish rubber less than awesome on wet roots/rocks. pretty good little rear tire though overall.