Wikipedia
ShredIt
ShredIt is designed to securely erase files in a variety of ways, using various overwriting patterns. Originally released in 1998, Shredit is capable of erasing files on Mac OS 7 through Mac OS 10.8 and later, as well as Microsoft Windows 95 through Windows 7 and later and iOS(sublicensed by Burningthumb Software). Versions of ShredIt are available for 10.6 and later through the Mac OS X App Store, earlier and alternate versions are available through the Mireth website.