It'd be nice if the Drive Wiper could wipe a physical drive entirely, and not just a partition. I was a bit surprized when I needed this feature, to find that a drive-to-be-wiped must have a partition. And not just a partition, but a readable partition: unformatted/RAW isn't good enough.
I'd like to see CCleaner to wipe the *entire* disk surface, which would also destroy the partitions, the partition table (useful if you need to move a drive to a machine that doesn't support GPT partitions...) and even the MBR. But for that to be possible, selecting a drive letter won't cut it, because drives don't have letters - partitions have letters. And sometimes not even, for example when they're mounted in a folder.
On a semi-related note: why is the Drive Wiper stuck on "formatting" with absolutely no disk activity?
On a semi-semi-related note: what is the best (meaning good enough) method for when you want to sell a harddisk as a second hand to someone you don't know?