Best Non Magic Items

[Prism]

Potion belt from FRCS allows you to draw potions as a free action which means you can move to a fallen friend, draw a healing potion and pour it down their throat in a single round

A triple weapon capsule container from complete adventurer lets you apply substances to your weapon with a swift action. Fill it up with quicksilver (lasts 3 rounds), poison and ghostblight (non magical ghost touch 3 rounds)

oh, and an alchemical lab

 

[smilinggm]

one of my personal favorite non-magical item is the Adamantine Portable Battering Ram.
I havent found a door that can stand up to it.

 

[Foodgeek]

Ball bearings, caltrops, various kits and tools (healing climbing, and anything you're proficient with) and poisons. Silvered weapons (including arrows). hunting trap, acid, keg or flask of alchemist's fire, oil, mirror, magnifying glass, spyglass. vials and bottles.

 

[GreyLord]

For Low Level Characters...

War Elephants. Yes...WAR Elephants are good.