I recently bought LG G3 and I have enabled debugging mode but Eclipse is still not recognizing it, back when I used the Galaxy S3 for development I had to install Samsung Ki
it seems that Eclipse shows the offline mode for lg G3 and some newer devices and there is no way no use these devices for ADB debugging
there is a way
I am using windows 10
1- download this 11 MB file < http://dl2.uncox.com/android/upload/platform-tools-v22.zip>
2- then go to the directory that you installed the SDK
3- extract the zip file in to the platform-tools folder , override all files(click yes to all) be sure that Eclipse doesn't running
4- open Eclipse and select your android device that stands in devices tab at the right-top corner of your screen and then you can see the arrow near the screen- capture icon and you will find the reset-ADB. click on it ,after that your phone will ask you to allow android debugging for your device click on it
5- congratulations .now you can see that your device shown online
i hope this will help .sorry for my english