Bamboo point turner/creaser forms crisp corners and seams
This little, unassuming tool costs around $2 and is probably the simplest on my list. Its pointed end is used to poke the corner right side out when turning corners, and its rounded, beveled end smoothes out curves and seams.
The tool's soft, bamboo wood minimally stresses the fabric and stitching, yet gently helps form a nice, crisp corner, curve, or seam. You can even use it as a pressing tool, inserting it into a point or curve, to shape the fabric as you press over it.
My mom has a plastic one she got at joanns, but can't remember the name. point turner?