[bandersen]

I'd say a good DMM/VTVM is by far the most usual piece of equipment. A HV adapter probe is nice to have too. A scope can also be very handy for troubleshooting.

A test pattern generator (or just a good RF modulator) too. I've seen a lot of cases where there seemed to be video or audio issues and it turned out to just be a bad RF signal feeding the set.

Specialty items like a yoke and flyback ringer or sweep alignment generator are generally not need to get a set up and running.