This is the best seam ripper or 'un-sticher' we have found. It is big enough to grip comfortably for long periods of time, yet small enough to fit easily in the palm. The rubber grip gives you a secure hold. The blade is very, very sharp, allowing cutting of threads with minimal pressure. A protective blade cover is included. Can also be used as a button-hole cutter (be sure to insert a pin as a 'stop' so you don't cut the hole too large).
This seam ripper even works great to easily remove serger stitches, which can be difficult to rip out.
It's the only seam ripper we use now.
**Caution-blade is very sharp. Handle with care and keep out of reach of children.