What is your favorite one command block creation?

I remember a few years ago playing with several one command block creations, and there was one favorite called Weapons by the creator IJAMinecraft which worked with Vanilla Minecraft 1.8.9 and below. Essentially, this one command block creation placed items in the player's hotbar such as a bow and a bunch of spawn eggs. My favorite thing about this one command block creation were the spawn eggs, especially the squid bomb spawn egg which lifted a squid into the air and striked lightning to the ground with an explosion underground.