Cantrips

Well, with me growing up on AD&D. I thought cantrips and level 0 spells to be relative weak. Not in Pathfinder though.

Any class with Orisons or Cantrips has a steady supply of magic they can use. Casting 0-level spells don't use the memorization. Classes that prepare their spells memorized a list of 0-level spells, and then they can continue to reuse those spells over and over. The other classes (Bard and Sorcerer) that don't prepare just can cast any of their cantrips at anytime.

So for example, a cleric memorized Create Water, Light, and Stabilize. That cleric will always have the option to cast those spells... no matter how many times he casts them. However, if he needs to cast Virtue, he must rememorize a new list of spells. A more combative example is a wizard having Acid Splash as a memorized cantrip, each turn he can use his magic to deal damage in combat.

This ability makes magic-users always have a means to cast spells, and they never drain all their powers like in prior versions of AD&D.