Something you're just good at with minimal effort and/or you learned much more quickly than average.
For me, it's paper snowflakes. My brain just seems to effortlessly figure out what cuts to make to the paper wedge to make it turn out exactly how I want it. Largely useless, but good fun and was a much-needed ego boost when I was a kid :]
The second thing we have a big drawer with random sizes of tupperware containers and i just take the one looks like it fits and it is very close every time
I can do this as I’m drinking something - one gulp is roughly one ounce. Was especially handy with water fountains when tracking my hydration, but that hasn’t been relevant since 2019.