Since people just can’t help coming up with new, fun, unusual and experimental instruments, I’ll have to keep going with this series!
These showed up on my radar in the last months:
Sympath

The Sympath, created by Dave Riedstra, it is another take on the topic of string-resonance-based instruments. As it is described on the project’s website:
The Sympath is a string resonator / feedback instrument I am designing with help from collaborators Gayle Young and Mitch Renaud. The project is currently in prototyping stages
More info about it here: https://daveriedstra.com/sympath/
Also check out Dave’s build log, which he updates quite frequently: https://daveriedstra.com/sympath/blog.html
BLL Instruments Elyra 2
There is no shortage of ways to make your guitar sound like a synth, and in the past some attempts have been made in creating synths that you can play a bit like a guitar (the Omnichord comes to mind). The Elyra 2 takes the concept a bit further by allowing full strumming.
Vongon Replay
This one is not all that unusual: you get all the classic ingredients of a synth, like piano-keyboard, knobs and sliders. But the absolute lack of any labelling is still interesting.
https://www.vongon.com/products/replay
Keybird X1
Maybe not unusual in general, but for a piano it’s a bit out there. I mean… an acoustic piano you can carry around? Plus it has pickups and MIDI!
Ellitone Keycontrol
Not really sure how this works, but apparently it uses contact mics positioned under the touch bars, which is a cool idea!