How about Sports, Flyer mentioned sports and musical instruments.
I won’t force musical instruments but encourage and support is important for those so inclined. Neither parent can set the example as musicians.
Not necessarily sports but physical fitness is mandatory. Two of my kids are active enough, one isn’t. He is still reasonably fit but we fight too much about it. Doesn’t regularly go outside to ride bike or jump on the trampoline and bitches about family hikes etc.
Yesterday , he started swimming lessons even though he is a pretty good swimmer. Since we are driving the little guy we figured that he might as well take some lessons. He likes the water and it is his best place physically. So, I told him he had the choice to take up consistent swimming or running which he hates, until he was on his own. He chose swimming. He gets that consistency is the key. He doesn’t have to be a monster swimmer or anything just do it consistently and usually on a team(for support and fun). He’s pretty o.k. with it so far. I think he will actually enjoy it, it will be good for him socially and physically and I won’t have to fight with him to stay at healthy levels of activity. The whole change even seems like a happy occasion to him. My wife is very happy about it.