Who are some of Galactus's most notable Heralds, and what is their function?

Galactus often employs Heralds to scout for suitable planets for him to consume, thereby saving him time and effort. His most famous Herald is Norrin Radd, the Silver Surfer, who rebelled against him. Other notable Heralds include Terrax the Tamer, Firelord, Air-Walker, Nova (Frankie Raye), and Red Shift. Heralds are typically granted a portion of the Power Cosmic, making them incredibly powerful beings in their own right, but they often struggle with the moral implications of their master's hunger.