Largest cranial nerve
SOME KEY FACTS ABOUT CRANIAL NERVES 

Trigeminal is the largest cranial nerve.
Vagus nerve is with vague or extensive distribution.
Olfactory is the smallest cranial nerve.

iv) Trochlear nerve shows largest intracranial course.
       v) Buccal nerve is the only sensory branch of anterior division of mandibular nerve
       vi) Smallest branch of trigeminal nerve is ophthalmic. 
       vii) Smallest of three terminal branches of opthalmic nerve is lacrimal nerve and frontal nerve is largest terminal branch of opthalmic nerve.
Vagus
Trochlear
Trigeminal
Olfactory