22. Phasic Armor. When struck by an enemy, roll 1d20. On a 20, the enemy teleports 10' in a random direction. On a 1, the wearer teleports 10' in random direction. The teleportation can only take a creature to an unoccupied location and includes all worn and carried items.
One way I see that this could be used would be for the DM to state that the spells listed in the PHB are "well known" spells that any spellcaster could identify as a free action due to their studies/familiarity with magic over the years. Being able to cast them is matter of power and practice...
There are lots of little things these are going to be useful for:
* Filling out low-level loot piles in high-magic campaigns
* Tournament prizes
* Pick-pocketing nobles
Parties will find uses for even "useless" items. The creativity will help foster more interesting games.