My wife and I were moving across the country.  She was driving the van and I was driving a 1965 Coupe deVille towing a camper.  Well being a 65 Cadillac it got horrendous mileage when it was completely empty let alone loaded to the gills and towing a camper.  So consequently I ran out of gas and since this was pre cell phones I was kind of hosed.  

I was just hoping she would notice I was missing and come back and look for me.  After maybe 20 minutes of waiting a guy pulls up and asked if I need help. I told him what happened and he drove to the next exit got gas and a can and doubled back to give me the gas and wanted nothing for it.