Disable Notification Center on OS X Revision as of Sunday, 27 December 2015 at 07:27 UTC

# Disable permanently
sudo defaults write /System/Library/LaunchAgents/com.apple.notificationcenterui KeepAlive -bool false

# Enable
sudo defaults write /System/Library/LaunchAgents/com.apple.notificationcenterui KeepAlive -bool true

# Kill now
killall NotificationCenter