For people who see no strong Western tradition of clerics as heroes, I just want to point out that this is a relatively recent phenomenon. Until the 18th century, clerics were arguably the single most frequently depicted heroes in literature. Hagiography (the lives of saints, martyrs, etc.) was the most prevalent subgenre within medieval and early modern heroic literature. This literature, I know, had a hand in the making of D&D -- Saint Cuthbert, after all, makes the Greyhawk deities list.
If people are interested in some inspiration from the past for cleric heroes, there are so many excellent sources of holy men fighting demons, performing miracles, controlling animals, even controlling elements like fire and water. When I did a recent survey of early medieval saints' lives, I discovered about 35% of all D&D spell effects in these stories. Martin of Tours controls fire and makes it attack things; Saint Columban controls water in much the same way; Cuthbert controls animals...
If people are looking for good D&D cleric inspiration in literary tradition, I must recommend the Voyage of Saint Brendan, Life of Saint Columban, Life of Saint Cuthbert and Life of Saint Gall.