I will buy most things new, just because I grew up very poor and everything was second-hand to me. And as a direct result, shit I had wore-out much faster because people before me didn't take proper care of said thing, wore it out before me, or flat-out broke it and I had to make due with what I had. I make enough money now to get the things I want new for the most-part, because I make my things last. I take really good care of my possessions.
For things that don't really matter as much, I'll buy 2nd-hand... Like RAM, Gameboy games, Disc-based games... as long as I can look at the disc's surface before purchase, TV remotes, Game consoles, etc... But some things I want new like most other PC parts (SSDs especially, GPUs, CPUs, power supplies, motherboards, etc...), some furniture, blankets, etc.
And then some things I really don't mine being well-worn or broken-in are things like Baseball mitts, 3D printers, slippers, Kitchen utensils, and girlfriends.