MacBook Pro Yosemite hangs during boot
Safe Mode working means that it is likely that something you installed is preventing the OS from booting. Specifically programs you have added to start at login in your user account or other things you may have installed that adds kexts to the system.


Look in System Preferences > Users &amp;Groups > Login Items


Remove them all and reboot. If it boots one of them is the problem, add them back till you find which one it was.


Look in /Library/StartupItems


Drag everything out of there (desktop or a folder somewhere) and reboot. As above if it boots fine one of those was the problem.

It is also possible that something went wrong with the OS and something OS related was damaged. you could try applying the latest combo updater for your current OS to see if that helps.

If nothing there helps, either I missed a location for startup items or you may need to reinstall the base OS. But before you do that, boot in safe mode and backup your drive.