This is the very first thing I made in Fusion 360 and my very first Thingiverse upload!
I followed a great beginner's tutorial to make a star stamp, then I used what I learned to replace the star shape with the deathly hallows from Harry Potter. However, the star shape is pronounced with the area around it sunken in, whereas I made the bottom flat with the deathly hallows shape sunken in, so as to replicate other deathly hallows stamps I've seen online:
A future improvement would be to extrude the same shape on the top of the stamp but popping out rather than sunk in, so that you can easily see by the top of the handle what the resulting stamp will look like. However, that would require printing with the handle side up and stamp side down, which is the opposite of what I did so I could use ironing. Not sure how best to add pronounced stamp on top of handle and print well...would have to do some tests to confirm best method...
I've included the Fusion360 project file in case anyone wants it.
I printed with the stamp end pointing up and used ironing for the top layers to make sure the stamp part was as smooth as possible.