The "Han Solo Blaster" on the left in the sixth row is a P-96 Mauser pistol, called a "broomhandle" from the shape of the grip. It was often copied for Buck Rogers and Flash Gordon lithographed toys in the 30's and 40's.

The bracket holding the 'scope on makes it impossible to load, but I suppose it has an eternal atomic power source.

For exotic looks, the "knuckleduster" pistols of Space:1999 were really inventive.

Nothing can compare, however, with the TRULY exotic ray guns of "Flash Gordon's Trip to Mars". They looked like blimpy little space-sausages which were held and fired in a backhand grip over the knuckles and fired with a thumb trigger.

See Flash use one to get the drop on Ming at: