Not good enough?
Top of the list would be an entire bike. Oh, the bike was okay. But the frame was too small, the bike was too heavy and I just outgrew it quickly.
But the specific items I've replaced because the first wasn't defective, but not quite right for my needs and preferences (roughly in order of importance to me):
- Saddles -- If the saddle ain't comfy, the bike ain't getting ridden.
- Handlebar/stem -- Major bike fit/contact point for me.
- Tires -- If they don't hold the road and resist punctures the way I ride, they aren't right for me.
- Handlebar wrap and grips (Getting closer to nitpicking.)
- Pedals (More nitpicking.)
- Kit -- shorts and jerseys (Really nitpicking, although snug fitting kit is a bit more aero and better on days with heavy crosswinds.)
Sometimes I'll revisit saddles, handlebars and stems and discover they work for me now, perhaps due to changes in my physical condition, perhaps due to differences in bike design and fit.
I just switched back to a saddle I thought I disliked a couple of years ago. Now it feels great. But I've lost 10-15 lbs since then, so perhaps that was the key.