When was the last time when serious new instrument was invented ?

Composer Harry Patch was continually inventing new instruments throughout his life! 

Maybe/probably the harpejji:

@mikelavigne:::Hendrix did NOTHING NEW,he simply COPIED/Polished Link Wray's style!!!

Well... have you already seen/heard every instrument in this world? Why are you looking for new instruments? Go east, to the continent of Asia (especially) and you will find instruments (you’ve never heard of) that will blow your mind for many lifetimes...

Well, what makes you think we are not familiar with Middle Eastern, Indian and others instruments ? None of those by themselves exactly blow my mind.

The overall most impressive instrument is still human voice followed by, I think, piano.

I like Moog synthesizers a lot, by the way.