If you read the skill description from the pathfinder 1e reference document, you will notice that it says that intimidation affects "an opponent" and that their "wisdom modifier" plays a role. My conclusion would be that anything which has a wisdom modifier and is capable of comprehending your attempts at intimidation can potentially ...
Per the Pathfinder Core Rulebook, Intelligent items are treated as constructs. Which as stated are immune to mind effecting effects.
Intelligent items can actually be considered creatures because they have Intelligence, Wisdom, and Charisma scores. Treat them as constructs.
The Pathfinder FAQ states
Intimidate, in particular, is a mind-affecting fear ...