Flow charts are a required Systems Engineering tool for communicating a requirement or design. Here's an interesting and actually funny flow chart on the use of "Oh Snap"
Here's a more complicated but still funny that's been around for ages. The original is too vulgar for this family friendly site so I cleaned it up.
And of course the CLASSIC super complicated flow chart that destroyed the Neanderthals. Here's one of the conversations from one of the many Hunting Process Review (HPR) meetings they had.