I've been debating whether or not to find someone in the 501st or Rebel Legion who looks like a good candidate to send a Prop Shield to do just that.
It probably wouldn't hurt to ask. I was curious, because I hadn't seen much about light saber build requests recently.
In early 2015, there was this post by forstyjr:
https://forum.pjrc.com/threads/27861-Light-Saber-sound-card-project. It ends with the sound card being a little too big, and then nothing. Obviously the smaller footprint of the prop shield would help here.
And then in November, there was this post by Grimmdus:
https://forum.pjrc.com/threads/31349-Teensy-3-2-Lightsaber, and on another group:
http://forums.thecustomsabershop.com/showthread.php?18795-Teensy-Lightsaber. It looks like the sound stuff was working (using the audio shield) but then the focus changed to driving the LEDs, and getting into much higher power LEDs than your normal APA102's or WS2812's.
And there was this also in November by Jared Barney:
https://trello.com/b/1MbM08rb/long-hilt-teensy-lightsaber-project.
A month ago there was a posting on Reddit:
https://www.reddit.com/r/arduino/comments/44hybi/help_with_teensy_sound_installation/
Here is a DIY lightsaber kit that uses an Arm Cortex M3 and various things in the prop shield:
http://www.artekit.eu/diy-lightsaber-audio-board/. This isn't a Teensy, but somehow it came up on the google search.
Other than these, it seems a lot of people tend to use off the shelf solutions, either by just taking the toy sabers and harvesting the electronics as it, or using something like the ultrasabers.com soundcard.
Soundbible does have personal use wav/mp3's of the various saber sounds (
http://soundbible.com/tags-lightsaber.html), but I suspect a company like PJRC.com needs to be careful of such things.
Soundsnap has more sounds, but I can't see what the rights are to them:
http://www.soundsnap.com/tags/light_saber.