Mine is MMD which stands for MikuMikuDance and is a popular animation program to animate anime characters, usually dancing. Here is my favorite MMD. The song is Ikkitousen and the motion for it isn't AMAZINGLY human-like (but not terrible like Toxic's hilarious motion), so they did a really good job with camera work and lights to make it more realistic. Yes, this camera is custom and not a premade one.
I also like SHSH which doesn't really stand for anything but is a signature hash. A SHSH blob is Apple's way of controlling which firmwares you can install on your iPhone. Once Apple closes the signing window for a certain firmware, you can't install that firmware unless you have a SHSH blob saved for your certain ECID identifier on your device. I actually have a SHSH blob for iOS 12.1.2 which is jailbreakable, but I have been lazy to update from 11.2.6 because Electra is really working well for me right now. If there's anything I've learned from years of jailbreaking, it's DO NOT try to fix what isn't broken because it's not likely to go well.
I think signatures and certificates are really cool since I follow 3DS/Switch/Wii U homebrew closely and because I was the one forced to teach the class about SSL (did a bad job sadly).