I tend to agree with whoever said locker space shouldn't be limited, as it is always causing me a problem. And not like a difficult decision problem, but a "Scum the first floor of Ga'an Telet with a Tinker until I find the item I am looking for" problem.
My locker is:
Crystal Ball (same reason as everyone else on this list)
Sensation Stone (Usually for orcs and monster classes)
Dragon Shield, Avatar Symbol, Namtar's Ward (Because I don't want to have to go beat a vicious dungeon in order to try out a strategy I happen to think up)
And my last spot is in constant rotation while I am trying new things. Recently it has been: Alchemist's Scroll, Piercing Wand, Trisword, Martyr's Wraps, and whatever the Stoneskin amulet is called.