Selective Spell

Metamagic

Your allies need not fear friendly fire.

Prerequisite: Spellcraft 10 ranks.

Benefit: When casting a selective spell with an area effect, you can choose a number of targets in the area equal to the ability score modifier used to determine bonus spells of the same type (Charisma for bards, oracles, paladins, sorcerers, and summoners; Intelligence for witches and wizards; Wisdom for clerics, druids, inquisitors, and rangers). These targets are excluded from the effects of your spell. A selective spell uses up a spell slot one level higher than the spell’s actual level. Spells that do not have an area of effect do not benefit from this feat.

Source: Advanced Player's Guide