For me, the Leica Q camera. I've fallen in and out of love with photography over the years and it (along with a toddler who makes for a great subject) has certainly rekindled things for me.
I took a (film) photography course as a teen that initially sparked this interest, and received a secondhand Canon AE-1 film SLR camera as a gift from a relative. I had fun experimenting with this for a while, but when I went to college, I guess it didn't make the cut of things to bring with me.
While I was in college, I was somewhat aware that digital photography was emerging, but it was expensive and I was broke, so the photo thing was just shelved for a while. A couple years out of college, digital camera prices had come down and I had a good job so I treated myself to a Canon Rebel XT digital SLR. Having infinite film was amazing for experimentation and I got really into nature photography for a while.
Then, like everyone else, the camera that was always in my pocket (attached to my smartphone) improved to the point that I didn't find myself reaching for a dedicated camera very often. I got a Sony and then a Fuji mirrorless camera with the goal of getting something smaller than the SLR that would still produce noticeably better photos than the smartphone. They did, but I still didn't find myself using them often, and I sold them off.
Then, I guess it was 2016, I read Craig Mod's review of the Leica Q camera[0]. I become borderline obsessed. His description of "delight" in using the camera's controls nailed something that I hadn't previously known I was missing from the mirrorless models I'd tried. I wanted the Leica Q, but at a price of over $4,000, that was just a non-starter. I'd check in on prices of new and used Q's periodically, but couldn't justify it for a long time. Finally in 2019, two things happened: Leica introduced a refreshed Q2, and my first child was born. This dropped the price of used Q models and increased my willingness to treat myself to one nice thing while the rest of my life seemed to revolve around keeping a tiny human alive. I snagged a used Leica Q for $2,200, telling myself, "well, if I don't love it, I can probably resell it for about the same".
I think that was the last time I thought about selling it. The camera, as described by Craig Mod, is a delight. Making wonderful photos of my child is too. Maybe there's a psychological aspect here too as the camera was a big gift to myself at a difficult time.
I wouldn't recommend that most people buy a Leica Q (or Q2). They're ridiculously expensive and you can't even change the lens on it. But for a handful of folks like me, who enjoy doing mostly-manual photography with great controls and image quality, it just might be worth it.
[0] https://craigmod.com/essays/leica_q/