This is a batknife that I designed. It is based off the batknife seen in Barnacules Nerdgasm's videos on YouTube. I designed it myself in AutoCAD and will leave the STL and DWG files below. Thanks!
Use a fine resolution for a sharper blade. Use plenty of infill to make it strong.
Use a file or sanding block to sharpen it. The plastic wont hold and edge very well so you might have to do this a lot.