Besides the bass, amp, speaker, tuner, and keys to the van? Oh, there's the cassette with "Donny Hathaway Live" on one side and the live Aretha Franklin at the Fillmore album (with King Curtis' All-Stars). Can't go wrong listening to Jerry Jemmott and Willie Weeks on the way to a gig!
Spare bass
Spare strings for my bass
Spare guitar strings (and I once sold some to a guitard who broke a lot of strings and never had it together to go to the store BEFORE the gig)
Spares for every cable
An SM-57 microphone (even though I don't sing, it's still come in handy)
DI box
Spare 9VDC adapter
Gerber Multi-tool
Cable ties
Velcro
Adhesive bandages
Sharpie marker
Ball-point pens
Note pad
Drum key
Towels
15' heavy AC extension cord (it's 16x3 with a metal 4-way box on the end)
Spare amp power cable
Spare 12AX7 tube (and I always carried a set of 6CA7's when I had my Music Man HD-130)
Spare tweeter fuse for the Eden cabinets
Gaff tape (NOT duct tape, but real proper gaff tape)
Analgesic (generally VItamin I- Ibuprofen)
Self-evaporating hand sanitizer
Spare 9VDC batteries
Little kit of sockets, crescent wrench, nut drivers, screw drivers and pliers
Soldering iron and solder
Small digital VOM
LED outlet tester
Spare fuses for any amp I own
Mini-Mag light w/spare batteries and lamp
That pretty much covers it. It's been a while since I went through the bag.
jte