For me it is Cellular Automata, and more precisely the Game of Life.
Imagine a giant Excel spreadsheet where the cells are randomly chosen to be either “alive” or “dead”. Each cell then follows a handful of simple rules.
For example, if a cell is “alive” but has less than 2 “alive” neighbors it “dies” by under-population. If the cell is “alive” and has more than three “alive” neighbors it “dies” from over-population, etc.
Then you sit back and just watch things play out. It turns out that these basic rules at the individual level lead to incredibly complex behaviors at the community level when you zoom out.
It kinda, sorta, maybe resembles… life.
There is colonization, reproduction, evolution, and sometimes even space flight!
I think the butterfly effect is much more interesting when you think about incredibly far reaching effects that are essentially impossible to predict. Someone running late and getting into an accident might actually be relatively easy to predict.
Instead: someone reading this post is running late. Because of this a different car following behind them gets caught at a red light they shouldn’t have gotten caught at. As they hit the brakes for that light, their passenger lurches forward and accidentally sends a nonsensical text to their friend. Their friend reads that nonsense text, and in their confusion spills their coffee on the floor. A person walking by slips on the coffee, hits their head, and dies.
The person running late just killed a person miles away, and they have zero idea that it even happened.