Mega Phoenix

The Mega Phoenix is an item that appears in several games in the series. Similar to the Phoenix Down, it revives all fallen allies.

Final Fantasy VIII
Mega Phoenixs can also be refined to make Phoenix Pinions.

Final Fantasy X
It is also a Mix result by mixing Phoenix Down with various items.

Final Fantasy X-2
Again a valuable rare item, Mega Phoenixes will become available for free from the Alchemist Dressphere via the Stash skillset. However, unlike in Final Fantasy X, a Mega Phoenix will not restore all revived characters to full health. Instead, it puts them in critical health (admittedly useful with Cat Nip). It can also be used through the Mix ability.