This is a simple, but thus far effective letter opener. I ended up with this design after several alternatives failed to display any sort of durability (i.e., would begin delaminating or chipping after little use).

The model includes chamfers at appropriate locations to ensure it remains comfortable in the hand. It does so while maintaining a sufficient cutting angle for both durability and effectiveness in cutting. Note that, given the materials involved in 3D printing, the point is not of great use in cutting through paper on its own.

I printed this in ASA, though I imagine it could work with any number of filaments. I would recommend something on the more flexible side (think PETG) to ensure a longer lifespan.

For an updated version, I am considering: (1) adding mild serrations to the edge (however doing so may lower durability); and (2) rounding the tip to increase durability by removing the chance for tip to chip.

All thoughts/comments/suggestions are welcome as always. Thanks for taking a look and I hope you give it a go!