The biggest thing that comes to mind is finding 2 shiny Pokémon back in the day on my Pokémon diamond version without any boosts to shiny odds.
for those who are unfamiliar shiny Pokémon are Pokémon who have a different color. A shiny charizard is black for example. The odds of finding a shiny in Pokémon diamond are 1/8192. I randomly encountered a shiny ponyta and a shiny kricketot. Both were very cool experiences and to date I have never encountered another shiny without boosting my shiny odds.