I once set the PCs up against a group of six animated gnome skeletons riding on a zombie dragon turtle through the Negative Energy Plane. The problem was, each of the skeletons had a bead from a necklace of fireballs and on their action they were each going to throw their bead at the PCs and "soften them up" so their master, a gnome lich, could then come in and finish them off. Instead, one of the PCs won initiative and lobbed a fireball from a wand at the zombie dragon turtle, engulfing all of the skeletons perched on its back and detonating their fireball beads.
50d6 points of fireball damage later, there was an unappealing blob of turtle soup floating through the Negative Energy Plane.
Johnathan