2081681993819799846994786333448627702865224538845305484256394568209274196127380153785256484516 (etc)
Numberphile · 19:36 · Watch on YouTube
Go contains more than a googolplex of possible legal games (10^10^108 or more), making this 2,500-year-old 19x19 board game one of the only real-world places where such a huge number occurs.