How about a Tesla coil. I personally feel that it is mandatory. It doesn't have to be very big!
On the other end of the spectrum, have you built a crystal radio? This is another elementary requirement. It seems magical to me to pull signals out of the air without needing your own power source.
Why not build a tube amp? There is no adventure in using audio amplifier IC's if you're going to construct your own circuits.
Use some imagination. Check out transmitters, motors, buzzers, speakers, nixie tubes, LED readouts, LED arrays, High-power LEDs, low-voltage DC incandescant lamps, voltage mulipliers, solar panels, batteries, robots, light organs, PC Interfaces, timers, clocks, logic games, electronic dice, heaters, a million more beyond what comes off the top of my head. Excuse me, but don't you dare come in here whining like that. Are you implying you have read everything ever posted on this forum? Now go away and don't come back untill you are ready to show us what you have done!