After seeing a few different versions and being unsatisfied with certain aspects of them I decided to make my own version. Using ChaosCoreTech's batarang as the basis I went for a central pivot point rather than the offset pins.
EDIT - 28/04/2018 -
Files updated with Left and Right batarang blade.
Misc notes updated to reflect this.
The print is quite a tight fit and will need sanding to get the folding action to where you want it.
Even though the blades are the same, a Left and Right blade have been included in the files.
I printed the pins with the bat logo facing the print bed so that supports weren't needed but found that on my printer I still needed supports so that the logo printed properly.
A small dab of glue will hold the pins together and aid the mechanical strength of the piece.