Cleric: None.
Crusader: The War Horse sounds cool and unique.
Warrior: None.
Dire Lord: The standard disposable skeletons are fine.
Ranger: Falcon for some utility, maybe to help expand tracking area or provide overhead view. Maybe even call on it for some special combat attacks.
Rogue: None.
Monk: None.
Summoner: Summoned elementals with impressive visuals. Allow dark and light summoning and mixing elementals.
Enchanter: Charm or enchanted armor/weapons. Enchant real weapons and armor, set to defend only.
Wizard: Familiars are fine.
Druid: Befriend animal type creatures
Shaman: Raise wolves and dire wolves
Bard: None. Instead of a charm song make it a confusion song.
Necromancer: Summoned skeletons or higher forms of undeath. Control undead (mind transfer). Raise corpses for short duration pets. More variety and more situational than the Summoner. Use 2 or 3 types at once.
Spellsword: None. :)