Lol, I don't have a favorite, they're all crap in my book due to my experience. But Bugera is only considered a fave because it has the sound and features I want (333XL).
Bugera = fire hazard (stock)
Mesa = Sounds like #### when turned up and not miced (too blatty)
Marshall = Too unreliable
Orange = again, too unreliable (dealt with my bassist's)
Peavey = Too unreliable, either that or the tone totally sucks nads
Gorilla = FAIL
Vox = Too boxy sounding
Ampeg = No Distortion without a pedal + Rare tubes
Fender = No distortion channel, would need a pedal...
SUNN = heard of problems will avoid
Crate = Too generic
Randall = Hard to get a good sound out of
Krank = Not enough channels
Bogner = Not Enough Channels
Epiphone = Crappy speakers and not enough watts
So pretty much, if all amp manufacturers disappeared, I'd probably just chock it up to become reclusive for many months, and build the ultimate amplifier myself. It'd have to be something 150Watts, have EL34 tubes, 3 channels, solo booster, Reverb, footswitchable everything, and have it's own 4X12 cab that is very bassy yet tight and crisp, and I'd probably go as far as to add multiple cab compatibility and the ability to mix cabs of different ohms with each other (built in mismatch box). Needless to say, I'd probably start off just making them in the USA, and slowly start having them made in other spots of quality, including Germany and Japan. Yes, I'm very very picky.