file shredder
WipeDisk - Portable File Deletion Tool

WipeDisk is a small portable secure file deletion tool. It can be used to securely wipe both logical and physical hard disks, USB flash memory sticks and micro sd cards. Supporting 14 unique wiping methods, this tool should ensure that your wiped or deleted data is securely shredded and no longer recoverable.
DPWiper Portable Secure File Deletion

DPWiper is a compact, portable file shredder tool that allows you to securely delete files and folders using simple drag and drop file destruction functionality. It supports both standard deletion and advanced wiping methods, including a one-pass overwrite (DoD 5220.22-M compliant) and the more secure 35-pass Gutmann method.
UltraShredder - Portable File Shredder

UltraShredder is a Portable application that allows a user to Securely Delete or Shred files. It does this by overwriting the information with random characters. If an attempt is made to recover the file or files that have been shredded using a data recovery program, only illegible information would be seen in place of the file.