And of course there were spark-gap transmitters as well. Other amusing items:

• mechanical rectifiers: basically a DPDT switch driven by a 3600RM motor.
• flywheel "capacitor" (for experiments involving sending enormous currents through a 1-turn copper coil -- you get a really high magnetic field for a few milliseconds before the coil either melts or explodes. Or both) The one I heard about was a 16-ton concrete flywheel; I don't remember the RPMs, but it took several days to spin up and stopped in a quarter of a turn.
• magnetic-core logic. That's another that will stand up to pretty serious doses of radiation, but I don't think it would handle EMP very well.