The Sprinklers
Half the fun of a hackerspace is trying new things you've never done before with minimal research and just seeing how it goes. Once upon a time some members wanted to cast their own wedding bands from silver at the old shop, and to do that they looked up the melting point of silver, realized that handheld propane torches burn about that hot, and gathered their materials for their intended wedding bands.
An interesting fact of metallurgy is that the melting point of a metal isn't the same thing as the temp where it flows smoothly and casts neatly. The couple realized this as they were able to get their silver to somewhat liquify and get maleable and crusty, but not actually liquidy and flowy. No bother, grab some more torches from over there. After quite some time and confusion trying to get their would-be-rings molten enough to cast, multiple torches trained on their small crucible, blazing away at not-quite-hot-enough temps, their attention was drawn elsewhere. The heat from their torches had been rising up and building in the shop's ceiling, where it eventually blew a sprinkler head.
After about an hour of flooding the entire facility, a visit from the fire department, and some very soggy would-be-silversmiths, the shutoff valve was found, and the flood was stopped. It is unknown if they ever reattempted casting their own rings, but new members to Freeside are commonly shown where the sprinkler and water shutoffs are.