For me, it's cars.
What sucks is being a car guy without a true enthusiast car... I lost my '04 Mustang GT when my daughter was 6 months old in a traffic accident (I was hit by a van, no crowds were affected, to borrow that old trope). That was more than 10 years ago. I haven't been back in a real car since.
I took the kids to a car show a couple years back and told my daughter, this is what I did before you kids came along.
I don't know if it was my tone, or what, she said something along th e lines of you're making me hate being born.
We left the show soon after she said that.
Any time I bring up even basic maintenance, it's an argument. I guess we dads are just mindless worker drones. If you're allowed your hobbies without any fighting, God bless ya.