I use an unholy mixture of random no-name knobbly black MTB tyres, plus a couple of Schwalbe Land Cruisers. I find the cheapos slightly grippier in soft mud, but the Schwalbes easier rolling on the road, plus I haven't suffered any punctures with the Schwalbes either. I've had several on the cheap knobbly tyres, but only ride those fairly locally where a walk home isn't too disastrous.