Diviner
A Diviner is a form of Specialist Wizard in Dungeons & Dragons. Their associated school, Divination, is the archetypical "utility mage" school; diviners have no offensive powers inherent to them, but their ability to gather lore and information is unsurpassed, with the ability to read minds, look into the past, see across the planes, and foretell the future.
Ironically, this has made Diviners one of the schools that DMs tend to hate the most, as whilst they don't directly benefit in combat, their spells A: make it almost impossible to run mystery or detective-themed games, and B: support the infamous "Scry 'n' Fry" school of boss-fighting.
5th Edition's Arcane Tradition
Diviners are still the typical DM's most hated wizardly tradition, and probably the one most likely to get banned at any gaming table. Why? Because the 5e Diviner is a master of screwing with dice rolls and is one of the more complicated of the default Traditions. At level 2, they gain the Portent ability, which lets them roll two D20s and take the numbers as notes. They can burn these "saved" rolls to use them as the automatic results of an attack roll, saving throw, or ability check, although each "saved" roll is only usable once, the Portent can only be used once per turn, and "saved" rolls are lost the next time the Diviner takes a long rest. At level 6, they gain Expert Divination; whenever they cast a Divination spell of level 2 or higher, they can regain a spent spell slot, so long as this slot is A: no higher than level 5, and B: is at least one level lower than the spell they cast to gain the refund. Their level 10 ability, The Third Eye, isn't so bad; when the Diviner completes a short or long rest, they can give themselves either Darkvision 60 feet, Ethereal Sight 60 feet, See Invisible 10 feet, or the ability to read any language. Finally, at level 14, their Greater Portent gives them three D20s for Portent instead of only two.