Here a few I did years ago.
1. I machined a long piece and cut what I needed for the muzzle section. At the time, K-Mart clearanced this pellet gun I had used for a base. I added some detail to the muzzle opening and instead of the cocking device that came with the gun, I sliced open and fit a ribbed tube section. The tube slides and allows it to still cocks.
2. I had a small piece of the milled metal I used from above. I noticed that this looked a little similar to the holdout blaster Mara Jade uses. I decided to see what I could do to make a cheap and quick blaster prop.
I picked up a water gun from a $2.00 set at Target
I dremeled the old muzzle off and sanded it smooth. I then inserted and glued a woold dowel to support the new metal muzzle.
Once the Muzzle was in place, I added some allen screws and a dew washers to cover up some printing on the handle. The trigger was modified to look less watergun like.
I added a piece of a faucet spout to finsh off the inside of the barrel.
Once painted, I weathered with sandpaper and paint
3. I picked up a squirt gun for 50 cents and cut off some section and covering holes with thin scrap plastic. I went through my junk box and found an old brass turn knob that I machined a few years back to use for the trigger. I used a replica graflex glass eye holder in the barrel section with a piece of an old pen I stuck inside. Below that is a fake LED bezel from an old Larbel Obi saber.
I used several layers of paint and wet sanded each layer. The main color is a color called anodized bronze. It is a dark gray metallic color. I figured that too many people use black. Using that color allowed me to us a black wash as to create a weathered look and help pick up the details.