I've been thinking about the spell
Fire Trap. Druids get it at 2nd level along with
Resist Energy So if a Druid cast Resist energy, they could stand next to an enemy open up the device, and have the enemy take damage but not the druid. I'm assuming that the same object could not be Fire Trapped multiple times. But I'm wondering if there are items that can all be opened at once easily, all firetrapped, and be used to do devastating damage to an opponent.
The disadvantage of course is the 25 gp material component which requires the Druid to burn his wallet to use this trick often.