Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
I'm talking about some tools, which comes in very handy while you are in trouble or save you from future trouble or even help you to do things fast.
FSlint is a very good utility to find duplicate files, bad names, empty folders, all that trash that you don't want to be on you file system. Install using -
sudo apt-get install fslint
TestDisk is a powerful undelete or data recovery tool. However it does not support ext4 yet. but still many distributions are using ext3, If you have any important data on your disk, then you should have this installed.
Install using -
sudo apt-get install testdisk