There is no ultimate weapon or armor but there are certain abilities that are hard to not see as awesome. I'll think on some items later
Weapons:
+5: A weapon that doesn't hit often and hard is useless
Holy or unholy property: Lots of stronger enemies have damage reduction against good or evil. Plus adding 2d6 damage against them is great.
Collision property: +5 damage against everything all the time is pretty sweet.
Force: Only works on ranged weapons but turning a weapon projectile into force, which bypasses almost all damage reduction, is fantastic.
Wounding: 1 point of constitution damage per hit can annihilate creatures vulnerable to it.
Armor:
Heavily fortified property: Stopping critical hits and sneak attack damage cold is wonderful.
Soulfire property: Protects against death effects, negative energy, nearly cripples an entire class of spells.
Items:
Third eye of conceal or ring of mental fortitude: Makes you immune to mind-affecting abilities (and some other thing). Shuts down an entire class of spells and abilities.