This tutorial will demonstrate how to make Samus' arm cannon with optional lights and sound. This was a prop I created for my Samus Aran (Metroid Prime) Gravity Suit.

I recommend watching some tutorials on building with foam first (such as Evil Ted Smith on YouTube) and some LED soldering and safety videos for some basics first.

Please give some love and a vote for the Halloween contest!

Supplies

EVA foam in 5mm and 2mm widths
Car vinyl or paint (I got my vinyl from Wish.com)
Contact cement (I recommend LePage brand indoor version)
Worbla's Transparent Art (or something comparable)
Orange translucent vinyl
Dremel (or other sanding tool)
LEDs in red, orange, and yellow
Wire
9V batteries
Switches
Soldering iron
Solder
Safety goggles
Resistors
9V and coin batteries
Scissors
Cutting mat
Blades

Optional:
MP3 player
Small speaker

Step 1: Draft Your Patterns and Build Your Shapes

The first thing I did was create a tube from 5mm EVA foam that fit around my arm reaching from my elbow to my fingertips. I glued it together using contact cement. Next, I traced out the next layer from reference photos, making sure everything was symmetrical (you can use a measuring tape for this). I cut that layer out of 2 mm EVA foam and covered it with a thin layer of contact cement to help the car vinyl adhear better. Once the contact cement was dry, I covered it with car vinyl, wrapping it around the back to cover the whole area. Next, I outlined where the piece needed to be placed, added contact cement to both pieces, and attached it.
If you choose to add LEDs to your Canon, make sure to cut a hole where they should go (shown in picture). Cover that hole with a strip of clear acrylic or Worbla's Transparent Art covered in the orange translucent vinyl. You can also choose to use any kind of orange plastic you can find. I repeated the steps until I had my Canon built up.
for the round pieces on the sides, I had to stand down two layers of 5mm EVA foam that I glued together. If you use vinyl, you'll have to cover that piece with contact cement, and when it dries, use a heat gun or hair dryer to heat a vinyl and pull it over the round edges. You will need to cut darts in the vinyl to fit around some edges. See my other tutorial on how to cover foam in vinyl wrap.

I added an optional removable missile to my blaster by again following the shapes that I referenced to make a pattern and adding magnets to attach it. Again, I used your Worbla's Transparent Art and orange vinyl to add pieces that would glow with LEDs. I used Worbla's Finest Art to create a sturdy base for it so it would attach nicely to the curve of the cannon. This needs to be heated with a heat gun in order to take shape.

Step 2: Inserting LEDs

I added a lot of LEDs in order to make my cannon glow very bright. Note that if you choose to use all three colours of red, orange, and yellow, that they are rated differently. I simply created two strands of parallel circuits to get around this. You will need a soldering iron, solder, and all the parts needed to connect the LEDs safely if you wish to do this yourself. Otherwise, another alternative is to use a set of battery operated Christmas lights. You can even paint Christmas lights the colours you want by painting them with stained glass window paint. This is available at many craft stores and works very well. I made sure to leave one yellow LED for the front light, and connect this piece last. Therefore, make sure you don't attach the front piece before creating your lighting system.
After I soldered my lights together, I used hot glue to make sure that my connections didn't touch by gluing them to white 2mm EVA foam in the pattern and spacing I wanted. This made them a lot easier to slide into place and glue down. I made sure to leave a lot of slack for the wire for the front light so that I could glue it in properly. I hooked everything up to 9V batteries, and therefore needed resistors (orange orange brown, to make things easy) to ensure the LEDs didn't burn out.
The small missile has its own LED system with four yellow LEDs and a coin battery (no resistors needed).
The images provided are a good reference for how to set this up.

Step 3: Adding Sound

I found the best way to add sound to a prop and have a lot of volume is to purchase a very small speaker with a headphone jack (available at most electronic stores or online) and attaching a small MP3 player to it with options to repeat sounds and buttons able to be blindly manipulated in the cannon. You can easily upload sounds from the video game that you would like to play, including music, and it will play very loudly with the volume all the way up.

I wasn't able to upload the video of the sounds here, but they're available on my Instagram at BrainstarCosplay.