I printed brycelowe's tape dispenser design, but the included printable tape cutter part did not cut the tape as easily as I hoped. To remedy that, I created a replacement part with a thin groove that accepts a serrated metal blade from a used-up roll of wax paper (Waxtex brand). This is similar in concept to mclambglass's remix, but only requires printing 1 replacement part rather than a complete dispenser body replacement. The replacement part is compatible with the other version 2.0 files in the original design. I re-modeled it from scratch by taking measurements of the original plastic_cutter piece.
After printing, I cut a piece of the blade strip to length, and flattened the original packaging attachment holes in the metal strip a little so that it would fit in the groove of the printed piece. I feel this does cut the tape more easily, so I'm sharing the design in case anyone else wants to try it out.
Amazon Basics PETG
I used PETG for the rest of the tape gun and this part, and really liked the combination of flexibility and toughness that it provided to the finished parts. However, I believe PLA or ABS (or any other rigid filament you can successfully use to print the tape gun) should work equally as well. I used 40% infill, but otherwise used standard Slic3r PE settings (notably: 2 perimeters, 4 bottom/5 top layers). I think a lower infill density would probably work fine, but it's a very small part and probably not critical to get perfect.
You'll probably want to rotate the STL 90 degrees around the Y-axis so that the slot for the blade faces upwards, opposite the bed. The little nubs that hold this part into the tape gun don't quite touch the build plate, but the gap is so small that my slicer wasn't adding any automatic supports there and the print came out fine.