One project would be a clock with Nixie tubes for time display. The project would involve some serious interface work (high voltages, no multiplexing possible) but the resulting "display" is nothing usual.

My idea of this is to have a polished stainless steel (or brushed aluminium) box with four nixies on top.

Another "clock" would be the kind that Rowlings created on Weasleys wall. (Harry Potter). Requires some work with stepper motors but again - should look really nice.

One unorthodox project I have done was a guitar amplifier with a MCU taking care of the bias of the power pentodes. Usually this is done by selecting a matched pair (quadruples the price) and then adjusting the bias by hand. My solution measures the anode current and gain and then adjusts the bias and phase splitter balance accordingly.

I lended the amplifier to a friend of mine and he was very pleased with the sound. Things got worse when he learned that there is a microcontroller involved with it. Immediately he started hearing a certain "metallic" sound on it ....

Last but not least - have fun with it and do not take too "easy" project. At least I would not - no challenge == no fun.