I'm running a 44T chain ring with the Rohloff 16T cog mounted to a trusty Race Face Turbine crankset. The 44T is really unnecessarily high, but it's what I had on hand at the time of the build. I'll be replacing it with a 38T or 40T which will provide a more appropriate gear range.
A Rohloff Chain Guide keeps my chain in place. Not absolutely necessary, but it's a nice design and not worrying about my chain coming off is worth the cost.