There are all sorts of strange equipment items you pick up during the game. Don't worry, you can't "miss" one. Just keep playing and you will get whatever you need before you need it :)

Armor
found - armor vendor on phoenix
magnaplate armor - 10,000 +33% armor
adamantine armor - 60,000 +50% armor
Aegis Mark V - 250,000 +66% armor
Infernox - 1,000,000 +80% armor (only on pass 2 of the game)

Refractor
found - Marcadia
reflects laser beams to open doors and slay enemies

Tyrrha Disguise
found - AmmuNation Nation
Lets you turn into a Tyrrha monster and talk with them.

Hyper Shot
found - before going to Daxx, on Phoenix
Have to pass the Helga Course
traditional hook shot swinging and tractor beaming

Hacker
found - before going to Daxx, on Phoenix
Have to pass the Helga Course
break into computers to pass through doors, etc.

Gravity Boots
found - at the end of Blackwater City's battle
Lets you walk up walls that are metal

Bolt Grabber
v2 found - Zeldrin Starport
Sucks in bolts from a further distance

PDA
found - Quark's hideout for 250,000
can order weapons and ammo from anywhere

Shield Charger
found - Aquatos, near end of game
free with memory card
upgrades to tesla barrier

Charge Boots
found - Daxx, at top of pillar right by entryway - hop up around the rocks
Lets you run super fast

Nanopack
found - Zeldrin - use hypershot to get up to central area where path bends south


Ratchet and Clank 3 - Up Your Arsenal Walkthrough