Forensic scientists at the University of Leicester (UK) and Northamptonshire Police (UK) have announced a way to recover fingerprints from fired shell casings. The technique involves the use of an electric charge to attract an electrically conductive powder to the minute amount of corrosion caused by handling the shell casing. The act of firing the bullet actually improves the ability of the technique to recover the print. For more information, see this article from Science Daily.
PS. On re-reading my post, I noticed that I did not supply any answer to the obvious question of "so what?". The reason this technique is particularly interesting is that it potentially provides additional forensic evidence that could identify participants in gun crimes. Imagine being able to re-open a "cold case", for instance a drive-by shooting, using nothing more than a spent shell casing (and a fingerprint database, of course). Hopefully, there will not be any hidden "gotchas" in the details and this technique will be able to fulfill its initial promise.