In World of Warcraft besides the two level 70 characters and the mage I'm leveling up, I have two bank alts. One for stuff I want to store for later, one for storage and trading on the auction house. I'm a hamster. I got so much stuff stored that I was considering turning one of my bank alts into a one-man guild and using the guild bank as additional storage. Yesterday I noticed I had several bags overflowing with cloth, from linen to netherweave. I ended up sending 180 each of wool, silk, mageweave, and runecloth to my mage and handing them in at the respective cloth quartermasters of Undercity, Orgrimmar, and Thunder Bluff for a quick 50k experience points (which got my mage up to level 55). And I *still* have lots of cloth stored.
I also have at least three 24-slot herb bags plus two normal 16-slot bags filled with herbs. I have 3 bags full of gems and metals. I store all sorts of hand-in items, like the stuff you hand in for Scryers or Aldor reputation, or unidentified plant parts for Cenarion. I try to keep my inventory of gear low, selling everything I don't wear, and I don't really have several "sets" of gear. But there are still a couple of items like trinkets gained from quests or the drakefire amulet that gives access to Onyxia that I wouldn't want to destroy, because you can't get them back. I destroyed most of the various holiday event items, like the winter veil disguise kit, but kept the most "fun" ones, even if they don't have any real effect. I have so much stuff stored, sometimes it's hard to keep an overview.
I would love if I had additional storage space for gear, in the form of several manequins to put gear sets on. One tanking gear, one dps gear, one fire resistance gear for example. Or for my mage where I have already bought "of the frozen wrath" gear for future levels.
How about you? Is your inventory squeaky clean or are you a hamster with several bank alts? What kind of stuff do you keep, and what do you destroy?