I see that you already used some space discovery utilities like Daisy Disk and Disk Inventory (X?). Therefore I find it difficult to throw in another tool to try.
Generally there are two ways of finding out where your hard drive space went: manual and automatic.
"Automatic" are tools like you used including Daisy Disk, Disk Inventory X and WhatSize among others.
"Manual" would be that you go through your folders manually either in Finder right-clicking (or Ctrl-clicking) them and select "Get Info" or using Terminal (if you are not afraid of the command line) and see which folders are using up the largest space. Once found, you go into the folder and do the same again.
For Terminal, you can use the following commands:
du -chxd 1
Repeat the last two commands until you found the items of interest.
cd / will change into the root folder of Mac OS X (the best place to start looking really)
du -chxd 1 will list down folders with their respective size. The "-chxd 1" options I provided will provide a size total at the end (-c), list sizes in human readable format (-h), limit the search to your system drive (-x), so that external or network drives are not searched and finally will only list the contents of the current directory (-d 1), which makes the amount of data better to wield. Totally optional, but recommended, after finding a directory to go into, change into it, then clear the output screen of Terminal (Cmd-K). That way you do not accidentally go through folders you already looked through, saving you some time.
To remove a file or a folder, type in:
rm -R folder_to_delete
If you are not the owner of a file/folder, you will run into an error when deleting a file. To overwrite this, you can prepend
sudo to the remove command earlier.
IMPORTANT: Please make sure that you know what file you are removing. Removing system files inadvertently leaves you to re-install the OS again, which may be cumbersome and lengthy.