I used some old Kenda Slant Six MTB tires. Not normally being an MTB guy I was surprised how much extra grip I had climbing short sharp rises. They don't last as long on pavement though, and are noisy and slow.
One tire I found to be very poor is the Schwalbe Marathon Supreme. Most road orientated tires will be semi-useable in general on gravel roads or trails, but the Marathon Supreme really wasn't suitable at all. I fitted them without really thinking it through on my last trip.