This is my favorite one. It is called the "Sharpshooter Rifle". Go to the next pic and you can see that it is made to rest on walls.
You mat remember this gun from episode 16 of the Clone Wars. This is a Z-6 Rotary Cannon. It shoots up to six lasers at a time.
This is a "Heavy Duty Rifle". The gun is used for infantry troops who work in "fox holes". After the Clone Wars the Imperials used the guns for the first to kill the Queen of Naboo who at the time was hiding wanted jedi.
This is a "DC-24". It is light weight and is made for special operations. This one was easy to design.