X̂
X̂ is the Latin letter X with a circumflex. The letter is used in the modern orthography of the Aleut language and in the current Alaska [Native Language Center] alphabet of the Haida language. In both cases, it represents the sound.
In mathematics, x̂ often refers to the unit vector in the +X direction. In statistics, it can also represent the predicted value for x, consistent with the hat notation.