I don't use clerics in my campaign right now. The two reasons for that are that I try to spread healing ability around for the classes. Barbarians, Rangers and Paladins all can heal to some degree, and everyone is able to do 1d4 hit points of first aid after a fight.
The second reason is that I don't run undead in my campaign. For one reason or another, the undead really just aren't my style.
With no undead and no monopoly on healing, there really wasn't a good reason to have clerics in my campaign.
Lately, though, I've been thinking more and more about fungi as monsters. This got started because of all the awesome monster fungi in Matt Finch's "The Podcaverns of the Sinister Shroom"- the titular Sinister Shroom, Pod-men, Fungemoths… really cool. Thing is, fungi are kind of (and I do mean kind of) like the undead. They aren't plants or animals, and they feed on death. There's something creepy about them, at least when they are not served on pizza; that creepy factor increases a lot when you have giant mushrooms, sentient mushrooms, mushrooms with unpredictable effects, etc. I've been thinking about ways to incorporate fungi into my games and one recently presented itself as a link on one of my friend's Facebook pages.
Apparently, there is a genus of fungus that infect insects with their spores, take over their brains, kill them and then sprout from their dead bodies. Cool! The ones that feed on ants and sprout just from the head are extra-creepy.
How's that for a zombie apocalypse? Villagers just start shambling off- away from the village instead of toward other living things- and die, and then a giant mushroom sprouts from their heads! How's that for unsettling your players? Of course, you can do all sorts of other things with this. For example, since the cause of the zombies is a fungus and not a necromancer of some sort, the players will have a terrible time trying to identify and neutralize the source before they, too, get infected.
If your games do involve the undead, then you can throw your players off even more. Imagine the look on a player's face when his cleric can't turn a bunch of low-level zombies!
Which brings us back to clerics. While the undead are really not my style, fungi are. What if clerics turned fungi- weird, dead-feeding, sinister things- instead of undead? Hmm, this merits further pondering…
Have you ever used fungi in your games? How did it go? Would you ever let a cleric turn fungi zombies?