Currently GParted allows to 'delete' or 'format' a partition. Unfortunately, most users are under the false impression that deleting/formatting a partition also wipes out the underlying data, which isn't true. [1] 

I would like to suggest a "fast" secure deletion method that overwrites data on a partition as suggested in [2]: 
dd if=/dev/zero of=/dev/sdx bs=1M

This could be added either as an option before re-formatting a partition. Or it could take the form of an independent menu item 'Partition > Wipe Data...' that would ask for confirmation and explain why this is useful, that all the underlying data would be irretrievably destroyed and that it might take some time for completion. The simple method suggested above should be as quick as your disk is. 

I believe it would be rather straightforward to add such an item, and it would be quite useful for users needing to (not just reformat a partition/device, but) destroy the underlying data on a partition. I make this feature request as this week I've used PhotoRec [3] on an old USB drive and I was quite shocked at the number of files that I could recover, and that I thought were throughly deleted long ago. 

[1] http://en.gentoo-wiki.com/wiki/Secure_deletion
[2] http://en.gentoo-wiki.com/wiki/Secure_deletion#The_fastest_way
[3] http://www.cgsecurity.org/wiki/PhotoRec