I like my Hickok 6000A tester. It will test all the common tubes, as well as diodes and transistors. It will test dynamic mutual conductance, shorts, gas, continuity... The whole bit.
I was lucky and got mine for free. I was working in the engineering department back in college and they needed help emptying out the chemistry building stockroom in preparation for remodeling. As we were hauling items out to the big dumpster, I saw a small red suitcase-like box with an electrical tag on it sitting next to it. I opened it up and it was a tube tester! I asked if it was to be thrown away, and was told it was- if I wanted it I could have it.
After replacing a few paper capacitors and locating owner's manuals, it has served me well.