Druid... or Cryomancer... choices! Does a cryo-druid count, patrolling Skyrim's snowy forests?
In terms of schools I'd be all over the place, but I'd only used specific types of spell from each - probably the calm, flesh, frost (rune/cloak), atronach and healing ones. Then console-command myself some cool ones like the the spriggan swarm and eject-push, and run around with an army of spiders and atronachs!
Not to say I'd disregard technology - I'd probably hide out in a Dwemer ruin and mess around with rubiks puzzle cubes all day, while whirling around a crossbow...
Conjuration, Illusion, and Mysticism. Coupled with a Dagger and some Enchanting. How scary you could be...
Appear out of nowhere to slit someone's throat, run away, dissapear, and go back to raise the ones you killed.
Twist the minds of those who are still alive, making them fight their undead friends; you don't even need Fear because you ARE Fear. Manipulate the mages with Mysticism; sap their mana using absorption, dispell their lights and shields, raise their dead, kill their living. Make them shit their pants.
The synergy Mysticism had with Conjuration and Illusion was unbelievably powerful. :D
Pyromancer, there are so many practical applications to summoning flames beyond just the offensive. Plus it's my favorite way to play Skyrim, and most other RPG's where the ability is available. So if I was on Nirn and had an aptitude for the arcane I would definitely pursue pyromancy.
Whatever the Elder Scrolls equivalent of this is: The Master Magician
That looks like a virus, Phil. I suggest checking your system. DrWeb CureIt is a nice free utility for that: https://www.freedrweb.com/download+cureit+free/?lng=en