The nerdiest thing I've done so far this month was to hack a Fisher-Price Wake Up and Learn "coffee mug" toy.
I ordered it for a toddler in the family; when it arrived my wife & I decided it was WAY TOO LOUD, enough to earn the animosity of the parents.
So I spliced in a 1KΩ audio taper potentiometer (volume control) so it could be dialed down. Hot melt glue attached it. As a nice bonus, I was able to align the shaft of the pot with a packaging mounting hole on the bottom so you can fit in a small screwdriver and don't have to crack it open to adjust the volume. If I were doing it all again I might order a 2K pot or one with an off switch for the times when complete silence is wanted.
