My dental aligners :(
I've been trying to get braces since I was a teenager, so long that I kind of lost sight of why I wanted braces. I was almost 30 when I finally took my savings to an orthodontist and told him I wanted braces, and he told me that the aligners would work better than braces.
And he was right. That's not the problem. I got so caught up with the general idea of braces that I'd forgotten that my goal as a kid was to fix my jaw, not my teeth. Even braces won't do that at my age. Those savings would have been better spent on surgery.