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
To contribute to possible solutions for this fix: I am using an LG G3 on a Mac.
In my case, ADB saw it as a device when I checked, and the Mac showed the device information in the System Information window, yet Eclipse did not see it. I also did not get the RSA confirmation pop-up when I connected the device through USB.
To fix, with my G3 connected, I selected the USB PC Connection (either from the navigation bar or through the settings) and changed it to be Send Images (PTP). Once this was on, I was given the RSA pop up and Eclipse recognized the phone in the Run Configurations window.