[bryukh]

My favorite for anyone interested in cellular automata optimization is Golly (http://golly.sourceforge.net/). It uses the Hashlife algorithm, which can simulate enormous patterns by caching repeated blocks. While other implementations might be prettier, Golly's ability to run complex patterns at incredible speeds makes it the go-to for serious exploration.

[drpossum]

Why is this the best one?

[bryukh]

For me, because of the algorithm and implementation, plus they have clients for different platforms with open-source code. Plus you can explore other cellular automatas.