The most critical safety feature is insulation. If you are working near live electrical lines, a wrench with 1,000V rated insulation is a non-negotiable safety requirement. Look for wrenches with a lanyard hole for tethering, which prevents tools from being dropped from heights and causing injury to those below. Additionally, features like an ergonomic handle and a built-in hammer with a smooth strike face are designed to reduce user fatigue and provide a safer, more efficient working experience.