Best: 2 pairs of quality headphones (a pair for gaming and a pair of Bluetooth ones for listening to Spotify on my phone). They both cost a good sum but I've been using them for several years now. I would normally have gone through several pairs of lower quality ones so I'm actually saving money already while enjoying top notch sound quality.
Worst: electric scooter. I jumped on the scooter bandwagon and bought it. Used it daily for 6 months. Now it's been tucked underneath my bed for 2 years because I went back to using my bicycle which is safer, healthier and more practical since I am not limited by the battery capacity.