A fixed or singlespeed wheel with an A719 rim is about as bombproof as bombproof can get.

For gearing, I like to have my fixed gear bikes to be just slightly higher than the gears I tend to wear out on my dérailleur bikes So on my Surly crosscheck, I like to use 48-19 and 36-14 the most. So one of my fixies has 40-15, and the other has 39-14. If I flip the wheels, they have 17 and 16 tooth cogs respectively.

Which brings me to the use of a flip flop wheel. It's nice to be able to flip the wheel around and have an easier gear to use if it's windy.