Mucocele is commonly seen is sinus -
Frontal
Maxillary
Ethmoid
Sphenoid
A mucocele is an epithelial lined, mucus containing sac completely filling the sinus and capable of expansion:

Mucocele are most commonly formed in Frontal sinus followed by ethmoid, sphenoid and maxillary sinuses.
Mucocele of frontal sinus presents as a swelling in the floor of frontal sinus above the inner (medial) canthus. It displaces the eyeball forward, downward and laterally.

IOC = CT scan
TOC = Endoscopic sinus surgery
According to Dhingra,

Least common sinus assopciated with Mucocele formation is sphenoid.
But Scott Brown says:

–– Most of the cases of mucocele of sphenoid sinus are referred to neurosurgeons. Therefore, it seems it is less common but actually the sinus least involved by mucocele is maxilla.