Zombie thread!
Two basses - typically a Thunderbird and a something Fender-ish, although it's usually an Epiphone/Squier pairing so if a loss is incurred it's not something irreplaceable. If I am forced to carry only one bass, in order to have everything covered I will bring the Frankenstein P-Bird (P-bass with Gibson TB Plus at the bridge). There are, of course, specific situations where I don't adhere to the standard, and anything is possible.