Frostfire Bolt

Frostfire Bolt is a Mage ability that came with Wrath of the Lich King. It is used by Fire and Frost trees. Fire can use it as a primary nuke in place of Fireball, Frost uses it as a proc from Brain Freeze. It gains benefits from talents that affect both Frost and Fire damage.

Glyphs
Glyph of Frostfire adds a DoT-effect to Frostfire Bolt that stacks up to three times per target.

Elementalist Spec
Before Cataclysm, Frostfire Bolt enabled mages to play an Elementalist spec. With the way the talents work now, this is no longer possible.