If the shit hit the fan, what test equipment would be in your bug out bag? Lets assume you can only take what you can carry on your back... so no Tek mainframes. Also it should be water resistant, and also be able to survive EMI from a gamma ray burst, EMP, or solar flare.
As a kid I remember having a radio shack pocket multimeter, but I recall it wasn't really that reliable and the battery was always dead when I wanted to use it.