This is the shape that most people might associate with the term "boomerang", I assume - as in "Australian gift shop".

It is a pretty decent flyer. Throw not too low and with little to no layover. If it feels a little sluggish, you might want to try and make it thinner, i.e., scale it down to about 95% along the Z axis.

How I Designed This

Made in Onshape. Have a look at the Onshape document to see how it was made.

My original design was a little too thick and a little too narrow, so I introduced two variables xyextra to make it a little wider and thicknessfactor to make it thinner.