Active traction could also help, but that's different than the rear locker. If you have one with the TRD-off-road package it has the rear locker. If you have the TRD-sport, it has a rear limited slip which is helpful but not quite as effective.
Yes, some cleaty tires will be a big help for mud and sloppy snow. Also, a winch, high-lift-strap combo or come-along is a big help--there are times when nothing you can do from the driver's seat will get you out, not matter what kind of tires you have.
You could also carry tire chains--they really help mud and snow grip.