Notification Center is one of Mountain Lion's coolest features, but not everyone likes it. If you want to get rid of Notification Center completely, OS X Daily shows off a simple terminal command to do just that.
First, open up Terminal (Applications > Utilities), and then type the following command:
launchctl unload -w /System/Library/LaunchAgents/com.apple.notificationcenterui.plist
Press enter and then type:
That's it. Notification Center and its icon should be gone and you get back that precious menubar space. Head over to OS X Daily for the full guide and an alternate method.