Theater tickets, travel, Twitch subscriptions, concert tickets, Apple music, Corgi, art supplies, college classes for fun, hosting friends and family (food costs), good whisky, fountain pens and ink (currently on a no spend until I use up most my inks), tattoos, gardening supplies (this year we just may break even with the food production), eating out once or twice a month and treating our friends/family when it's our idea, movies, whatever my students are selling for fundraising, yoga studio membership, Playstation Network, HBO Now just for John Oliver, board games.
Monthly housekeeping and garden care have become necessary with my disability, but I still consider them an extravagance.
That said, we drive old cars, invest a good chunk of our income, and use the library like crazy. Our house is small and drab compared to friends (and MUCH cheaper because of that; plus, we love it), and a lot of the above is paid for by actively spending below our budgeted amounts for things like groceries, getting rebates, and cashing in loose change (that last one makes up 100% of my tattoo and fountain pen fund, for example).