Cool idea for a thread.
1) Running. 1:07:53 half/2:26 marathon (pre-super shoes). Nothing elite, but eliminates most of the general population.
2) Sea of Thieves. A relatively niche open world pirate video game (yes, it's about as nerdy as it sounds) where I have achievements that less than 1% of the playerbase have achieved. Most people play it casually so the "competitive scene" is a niche within a niche.
3) Hockey. I was a decent, by no means great player. But I can say from experience the crossover between running and hockey is very small, so the odds someone is better than me at both and also great at Sea of Thieves is astronomically low.