Equoid, by Charles Stross

Equoid is the second story I've read in Stross's extensive Laundry series.  The Laundry is part of British civil service, the part that deals with occult threats.  And the threat in this one is a doozy.  We get a lot of fun action as Bob Howard (not really), computer nerd and office drone, takes on unicorns.  I know I've read some similar stories but can't bring them to mind right now, so you'll just have to go read it for yourself.  Very good stuff.  Reminds me very much of George Saunders' CommComm, so if you liked that one you'll like this one.