I made an alarm clock that blows up capacitors to wake you up.
There are more details on the Github repo but it's made from an esp32-c3 as the microcontroller, with 3 capacitor slots. There are relays on each capacitor slot to put 15v reverse voltage on the capacitor, with 5.1 ohm resistors on each slot for current limiting in case the capacitor shorts out. I also chucked in an SSD1315 OLED to show the time and a menu to configure it, although there's a web UI as well. The esp32 also means you can fetch the time from NTP.
It also functions as a small heater since I used LDOs to step down 15v to 3.3v for the esp32, I was lazy and didn't use a buck converter circuit :)
If you need to take it to the next level, consider something based on a xenon photoflash driver. These aren't as common as they used to be, but they're still not hard to make. I had to make one of these a while back and ended up using one of those $5 LTC chips but that was appropriate for the situation; there are certainly other ways to do it. This will basically charge a 400V capacitor up for you, which you can then dump into the 5V part. High-quality 5V capacitors will handle small spikes of this. But using a big 400V capacitor will make a big spike, which is not kind to the other capacitor. (I must confess I didn't try blowing up a lot of things on the one I made, but it was medical test gear, not technically a capacitor-blower-uper, and I was on deadline anyway. I also had other, significantly more destructive, equipment available to me should that be the goal.)
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