ObsidianDestroyer: If you've ever been on a faction server and you hate people who make indestructible bases, this could be a good plugin as it allows explosions to break obsidian. You can control the durability, so that way it is still tough to break through, just not impossible.
EssentialsProtect is the only other good one. As the other guy said, use http://build.sk89q.com to get an updated version of the "Best Region Protecting Plugin"!
The best anti grief is called Grief Prevention. It doesn't just protect claimed areas, it also stops spam, spawn camping, and lots of other types of grief.
I think everybody lists too many plugins. Since the question was very general, I'm guessing the original poster didn't want RPG plugins, plugins that change game mechanics, plugins to change where monsters spawn, and all that (or else he would have asked for it). Here's what I'm guessing almost all servers want:
Anti Grief: Grief Prevention (plus TekkitCustomizer for Tekkit servers), or Factions for a PvP server.
Anti Cheat: NoCheatPlus and AntiXRay.
Everything else depends on the server owner's vision for the server. I don't disagree that the other plugins you all listed are super cool, but they're not for everyone, and this is a very general thread.
Hello! Can someone please tell me which is better: BOSEconomy or iConomy?
Essentials money is the best. It works with most things, It is like the google chrome of minecraft plugins. It works with almost everything. And it is one plugin since it comes with basic essentials. So no IConomy needed unless you find a plugin you just must have and it only supports iConomy.