Years ago I used to race R/C Boats. I asked a buddy of mine that flew planes what his most important tool in his box was. He pulled out a hefty bag and said "It isn't if you crash it is for when you crash to pick up the pieces" For working on my 1949 f1. My most important tool right now would have to be my air-compressor. Can't use the air tools/sanders with out one. What is yours?