If you're dressing up as someone iconic for Halloween, having the right voice can make or break your costume. Think about it—having a Darth Vader lookalike walk up to you and start talking like Alvin the Chipmunk would probably ruin the effect (and possibly be a little creepy).
Want to make your costume more legit? Try this DIY Arduino voice changer by Adafruit that lets you add custom voices and sound effects, and even includes a keypad for you to control them.
The project uses an Arduino Uno, an Adafruit Wave Shield, which lets you add sound to Arduino projects, and an electret microphone amplifier. You'll also need some basic soldering skills and a small speaker for audio output.
Once it's put together, you can upload prerecorded sound effects and the Adavoice sketch so you can make your own voices. It's worth noting, though, that since it uses an analog-to-digital converter, you can't change the pitch in real-time, so you'll want to spend some time messing with the speed of the playback to make sure your voice is ready to go before you get dressed up.
Check out the video above for more details on how it works, and the project page for more photos and the step-by-step process.
If you don't want to be Vader, there are plenty of other costumes this could work with, like Bane from The Dark Knight Rises, Iron Man, or, if you want to go political, Big Bird. What are some of your ideas?