I have a hard time letting go of all my stuff, so I've never really sold anything big.
If i don't want it, then I'd rather give it away to someone who i know which needs it.
And nor have i ever had a real urge to get something special, when it comes to anime and manga, then i just download it or read it through the iphone, some games can be pirated, while at the same time i can still afford all of the games which i really want.
I've got a huge pile of stuff which has just been in my room for ages, i do never use it, but i so don't want to sell it, because its my stuff.
I will for example never touch my silly games collection, never use that electric guitar, nor all the expensive branded skateboarding parts, but i cant let it go.