Druid: Shield of forest: Cover him in leafes making him (invulnable, more armor, hidden chose)
Crusader: Holy Blessing/Crusade: A glowing cross apears above the crusader increasing his hp and dmg (something) or maybe healing nearby units...
Demon Lord: Anger: The Demon lord gets angry, getting bigger. increasing strenght and dmg, fire at both his hands. Units will maybe run from him...
Dwarven Marksman: Trible Barrel Rifle: Allows the Marksman to shot 300% as fast as before, but with less precision or firering all rounds at same time doing huge dmg but only good in close combat.
Troll Hunter: Skrinking net: Cast a net on unit, every 1 sec it scrinks in sieze, when net is to small the unit will take dmg.... or maybe just explode of preciur if low life/ killed by ability.
Fire Mage: Flamming Home: Creates a fire in some tree or something.. then every 30 sec a fire minion will spawn from the tree in fire. Last 1 min and every fire minion last 40 sec. Increase durection with levels..
Assasin: Friend or Foe: Throw poison blade, doing no dmg. After random time or specific time the target will go into frenzy attacking everybody around him, when effect ends he will be back normal if he isnt killed.
Wolf: Fullmoon: Huge Increasing all of wolfs stats, dmg, hp and lowring mana, changing into werewulf. But only as long as ingame timer shows full moon.
Ritualist: Demon Triangle: The ritualist walks around creating a triangle, then starts summoning the demon under his control. If disturbed while summoning the demon will be spawned hostile to everybody.
Dream Walker: Nightmare: Combine this spell with sleep. First cast sleep on target. Then use nightmare to enter his dreams and spread fear. Lowering his stats.
Trap Artist: There is a realy good trap on this site: look in spell section.
But else: Sticking Hole: Spawning some bushes and leafes on a spot, when unit (freind or foe) walks over it, it falls down on some spikes or just activets some spikes. Dealing dmg. (and maybe other effects)
Ranger: There is always multiarrow.
Else camoflage, dicuese as target unit, use on a unit and instantly turning apperance..to the target units apperance
That was all.. or some hehe:
But as said look around in spell section, you get ideas....