(Is Mjolnir sentient?)Thor talks to it sometimes, and he's referenced it as having thoughts, but it could just be weird viking attachment to his weapon since I've never known it to communicate to anyone but Thor if it is indeed communicating at all, and it's ability to sense worthiness is usually referred to as a function of enchantment rather than an excalibur style ability to make a choice. It doesn't seem to have compunctions about being turned on Thor, anyway.
Still, Thor says it thinks things occasionally. "My mjolnir finds that funny, how about yours?"
"Can't you hear it laughing?"
^An exchange between two Thors who met because time travel.