Infinite mana (with only two cards)

[Birdbrain]

{Tamyo, the moon sage} + almost any mana producing instant or sorcery

[Birdbrain]

Oh. Than you could play any other red instant or sorcery an infinite number of times (mana producing instances and sorceries are in red)

[Double-O-Scotch]

{seething song} times a bajillion and an old school {fireball}