$ sudo apt-get remove gksu 

Uninstall gksu including dependent package

If you would like to remove gksu and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove gksu 

Use Purging gksu

If you use with purge options to gksu package all the configuration and dependent packages will be removed.

$ sudo apt-get purge gksu 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove gksu 

See Also,