[quote name='Fisheth' timestamp='1435669755' post='2811183']
Bring gaffa tape/batteries/spare leads and a spare bass (If possible) to every gig, never know when something can go down.
[/quote]
and a soldering iron
seriously though i do carry one of those small placcy flip top tool box thingys full of sort of electrical knick-knacks including but not limited to, soldering iron and solder, gaffer tap, leccy tape. connector blocks, spare fuses, mini screwdriver allen keys, a few odd screws and spare jack plugs and stuff - doesnt take up much room and leave it in the boot of the car until needed
recently proved its worth to me personally by allowing me to repair a disconnected wire inside my J knob panel and thus prevented me from having to play the entire gig on the 'other' bass (a fretless)