Spells I use all the time...
Distortion is the school of Magic I use the most:
Mass Haste (normally on turn 1)
Stone Skin
Trap
Target
Phantom
Turn Back Time
Turn Back Time is just insanely good. I normally don't use level 5 creatures, so I only need level 2 of this spell. I have had a lot of success with Hasted Horsemen charging straight into the midst of the enemy, soaking up two turns of damage (enough to nearly kill the stack sometimes), before casting Time Back Time at the level of turn 2.
Order:
Helplessness
Healing (for level 5 units)
Dispel (we all know why this spell is necessary in AP

)
Chaos:
I don't bother with Chaos as a Warrior due to low Intellect, but as a Mage with 40 Intellect and Higher Magic, it's a different story.
Fire Arrow (5 mana, even at level 3?

)
Ghost Blade (10 mana but no burning. Good for bosses)
Fireball
Fire Rain (if I can find it)
I also use Sheep and Demon Portal sometimes.