Lots of toys now take batteries, and make annoying sounds. For years parents have dealt with this by taking out the batteries, which I approve of. But here's a toy where the batteries are essential:

The big gear in the center turns when you push the button, which sets all the other gears turning. It's a lot of fun, except for the music. It's not that it's especially bad music, but very few 20-second snippets hold up to this kind of repeated listening. So I opened it up and cut the wire to the speaker. Now it just goes "whirrrrr," which is interesting enough for Lily and much less annoying for us.

At a much higher level of complexity, the DPI (screen resolution) on my phone was set to make things super detailed but much bigger than I needed:

I'm willing to trade off some size and detail in order to fit more on the screen at once, but on Android there's not typically a setting for DPI. You're just stuck with whatever the manufacturer sets. But it turns out that adb shell wm density DPI lets you change the DPI. I lowered it from 640 to 540, which is still really high, and was much happier with the tradeoff between size and screen space.

Update 2017-04-15: my phone upgraded to Android 7.0, and switched back to the factory DPI. Running the adb command again fixed it. I'm now trying out a DPI of 500, to see slightly more on the screen at once.

(Earlier: hacks for my Yamaha keyboard and Razr M.)