i carry lots of adapters….bnc to rca (rarely used), USB extension cables (3 of these), serial cable, null modem serial cable, extension serial cable, various serial port adapters and extenders.
I also carry a IR remote extender (2 small pyramid looking things) from Radio Shack. This tool has been extremely valuable for gear racks that are in a different room.
Also a few extra batteries, in case the clients remote control dies or if my accupel remote dies.
I also carry a 2nd laptop.