In the series of strange and unusual weapons;

Kongsberg Postførerverge [Mailman Sidearm] M/1846
[ Linked Image ]

In the early 1800's, there where a series of brutal robberies of mailmen in Norway. As a result of this, the Norwegian postal service started to employ armed guards from 1837. They carried pistols or sabres, and should "with courage and their utmost effort" defend the mail.
From 1846 the postal service also issued the M/1846 Postførerverge. A large dagger with a pistol barrel on each side of the blade, it would give standoff capability to mailmen, or improve the arsenal of a mail guard.
The weapon is Norwegian, but was supposedly inspired by a German design.

Fortunately, Norwegian postal workers have much better psychological record than their US counterparts.

I've read a bit about these, apparantley the balance is awful, and they aren't particularly great as either a pistol or a dagger. Although I have seen a pistol-grip sword somewhere, but I don't remember where. Might have been the Metropolitan Museum of Art.

Probably a reason the bayonet became more prominent. Still neat though.

They are meant to looks scary, not be efficient :p

Similar designs can bee seen on some continental hunting swords;
http://www.myArmoury.com/albums/thumbnails.php?album=39

I like the mace/rifle combination; it looks like it might actually work, too! Thanks for the link!