Executioners always creep me out. It makes sense, they're legal faceless killers. To me that's the scariest thing about the executioner is that the man bringing the axe down on your neck or the hangman preparing the noose could be anyone, even your next door neighbor.
Fear the reaper because E is for Executioner...
Mercy Blades are an ancient order of executioners that operate in the free city. For centuries these masked men have served those in power, whether they be nobles born into power or elected officials. The sight of one of these silent, golden helmed brutes is enough to send hushes through even the busiest market crowd. They keep their identities secret. One never know if their silent punisher is kin or neighbor. The organization has been known to track down criminals that have fled justice, and it's said no man can escape the mercy of their blades.
Mercy's Axe (Masterwork Greataxe)
Damage: 1d10 (Small)/1d12 (Medium)
Weight: 12 lbs.
Special: If the target is bound and restrained the wielder may make a Profession (Executioner). If the check is successful the target dies instantly. If the check fails the attack is treated as a coup de grace. The main difference between a successful check and not is the mess the death causes. Also, unlike normal masterwork weapons, Mercy's Axes don't grant a +1 bonus to attack rolls. However, they do grant a +1 bonus to Profession (Executioner) checks.
*Technically Mercy's Axes are 320 GP like a normal masterwork greataxe. However, due to the nature of the Mercy Blades these weapons are never sold openly. It is possible to obtain them on the black market, but one risks incurring the wrath of the organization for owning one.
If using one of the classic D&D settings, Mercy's Blades are the prime material offshoot of Planescape's Mercykillers. If Patherfinder's Golarion is your setting then I would give them ties to the Chelish Hellknights.