Lagerphone’s are bizarre?
Quite a few can be found atWindworld - including the Daxophone (I am totally going to build one of those!). My favorite as far as names go has to be Barry Hall’s Hybrid Globotubular Horn.
I was amazed to discover there is a whole Mandolin family of musical instruments.
The butt flute and nose whistle.
Here’s Bobby McFerrin playing a theater slightly differently.
(Speaking of weird instruments, Bobby McFerrin.)
Since I was beaten to the waterphone, I’ll put out the Xaphoon, a cross between a recorder and a clarinet. Vienna Teng’s percussionist, Alex Wong, uses both, and a variety of other odd music-makers.
The same is true of balalaikas.
Not really an instrument and not particularly bizarre, but here you go:
A friend turned me on to Nosefluteat a party a few years ago. It’s as simple as whistling once you figure it out, but it’s always funny.
Not really bizarre but at least unusual,The Stick
Watched a demo at the Namm show and loved it.
One of my favorite homemade instruments - not for performance, but for practice - looks a lot like the Stick. It’s like a guitar head, tuner, neck, frets and strings, but no body. He rubber banded a stethoscope onto the back of it so he can practice in airports and on the plane without disturbing anyone with either the sound or the large size of a guitar in a plane seat, but he can hear himself play!
My ex is into unusual instruments. My favorite is the hank drum made from a propane tank, like this one. The one that gets the most questions and attention isn’t really all that “weird,” it’s just not played much in American music: the shruti box. (The steady drone is the shruti box, the changing tone is the singer.)
I love the fact that the inventor of this instrument was kidnapped and forced to become a Soviet spy-scientist. So surreal, yet true. 
The Tibetan Kangling…traditionally made from a human femur. And used to summon hungry spirits and demons. :eek:
Metal.