Basic Handle

I tried lots of variations to increase the finger comfort. Then I realised its best to use plain cyclinder with textured surface like dumbells.
Enable the “Fuzzy skin” option before slicing to create the grippy surface. Also I recommend using brim to increase the adhesion.

I used TPU-95 with 4 walls and %40 infill so it became pretty tough.

It's my first ever 3d design. You may want to change something, so the step file is included.