In article ,
Hobo writes:

Has there ever been an aircraft with a gun permanently aligned
off-center? I don't mean swivel mounted, but permanently fixed at a
point other than straight ahead.

Quite a few, actually. Assuming that you're willing to stipulate teh
defensive guns on bombers ranging from the Be.2C in WW I (ANd yes,
they did drop a few bombs) to the Tu-22M Backfire.

In terms of fighters, It's been done a number of times. The most
mentioned would be the upward-pointing "Shrage Muzik" guns on German
Night Fighters. This allowed them to formate on RAF night bombers in
the one quadrant with no lookouts or guns, and shoot into the largest
possible area - teh entire planform of the aircraft. The Japanese
tried something similar.

Wouldn't a gun pointed at a downward angle make ground attack easier?

Check out the Junkers-Larson ground attack prototype made for the
U.S. Army in the 1920s. It was basically an all-metal Junkers
monoplane transport with something like 30 .45 Calibre Thomson
Submachineguns firing at vatious angle through the bottom fuselage.
The idea was that it would fly along trench lines at low altitude,
saturating the trenches with bullets. (The opinions of the Gun
Plumber on board who'd have to change 30 75 round drum magazines after
each pass has not been recorded. Rest assured that it would have been
short, to teh point, disapproving, and contained a lock of words that
rhymed with "Duck".)

In the 1930s, the French built a large gunship with a downward firing
105mm Howitzer. From the 1960s on, the USAF, and several allied
nations, have flown various transports (C-47, C-119, C-130) with
arrays of guns pointing out of the side, aimed by maintaining a pylon
turn around the target. (Well, at first, at least) These guns have
range from 7.62mm machine guns to 105mm Howitzers, backed up by an
extensive sensor suite and ballistic computers. The side-firing bit
allows you to engange targets without flying over them, which is
generally considered a good thing.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster