My own suggestions on unique items:
] Sachiko Kotobuki's shirt.
'Just a shirt... or so it seems. It belonged to a female soldier who, apparently, was fond of nuclear weapons'.
It offers no damage reduction. Its durability is laughable, and it can't be repaired.
HOWEVER, if you detonate a thermonuclear bomb while wearing it... Surprise! You don't blow up!
\ Halkonnen Cannon.
'Eat Halkonnen, monster!'
It uses shells as ammo... But the shells, somehow, do a LOT more damage than normal shotgun shells.
It can only carry one at a time, though, and reloading takes AGES.
\ Vampire Gun
'For some reason, I feel this sting in my arm when I pull the trigger...'
Contrary to what the name could lead to, it is a melee weapon.
Every time you hit an enemy with it, you drain life points from an enemy.
BUT, if you miss, you lose some life points yourself.