This pistol is commonly referred to as the Assassin's Pistol, but was used by Sherese in A Plot to Kill a City before Buck got a hold of it to try to shoot Varek.
This little blaster is seen almost primarily throughout the second half the first season. I have not seen any official names for any of the pistols used throughout the series. Some of the guns/pistols that where used in Buck Rogers where also used in Battlestar Galactica. The base of this particular pistol was made from a Match-O-Matic butane gas lighter. It is shaped as a mini pistol which was a perfect starting point. The trigger and trigger guard were both removed and replaced with a new one that is more squared off. The barrel was unscrewed and removed as well. The wood sticker on the handle was most likely also removed and ribs where added down the handle then painted black. A clear acrylic tube was added for the barrel, so when the new push button was pressed by the actor, a bulb was lit for simulate the gun shooting. 
There are at least two variants of this pistol. The first one is seen above, the second had a safety catch added to the sides of the slide (I don't know how else to describe it)
