Drew Webber (mcdruid) is a UK Drupal developer, PHP programmer and linux sysadmin. This is his website.
This is a simple trick which (unless my googlefu simply failed me) I didn't find described anywhere when I had a quick look:
$ drush ev '$file = file_load(21749); var_dump(file_delete($file, TRUE));' bool(true)
I recently found myself trying to use drush to set up a Drupal 6 install on a server where I did not have root access. I kept getting errors along the lines of this:
Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 1234 bytes)
I didn't have permission to edit the php.ini file for php_cli, so I had to find another workaround. The solution's pretty simple and comes courtesy of the drushrc.php file.