Headsman's Axe

Description
 is a unique weapon in The Elder Scrolls V: Skyrim wielded by Ahtar. Ahtar uses it for executions, most recently in Roggvir's execution.

Information
The is considered a Two-Handed battle axe and takes both hands to wield, yet is affected by the one-handed perks and skill level. This item cannot be upgraded at a grindstone.

The same axe is used in your failed execution, however you cannot retrieve it from Helgen. You can retrieve it later on, if you do a quest for the headsman in Solitude. Go into his inventory and take it from there. It is also possible to simply steal the axe from Ahtar while he is sleeping in his house in Solitude, regardless if he is a follower or not (confirmed for PC).