Only significant items are detailed here; others are merely used to build other things, or are explained already on the Game Hints
Allows you to equip three Buster Parts rather than just two. It’s just as useful as it sounds; get this ASAP.
Refills your life meter. You can purchase extra packs from the Junk Store, and refill used packs there as well. Each pack restores one unit of energy when you use the canteen. A nice feature is that the canteen will not refill more than you need; any extra units remain in the canteen for future use. This is unlike Mega Man games where Energy/Sub-Tanks are used completely even if you don’t need all of their energy.
This helps prevent MegaMan from being knocked down by attacks. (Ignore what Roll says about falling great distances; it is impossible to receive damage in this game from falling.)
Equip, then hold
to Roller Dash. This allows you to travel faster and can be entertaining as well. If you jet off the edge of a ledge or other object, MegaMan will jump automatically; otherwise there is no way to jump while dashing. Control MegaMan with the control pad; press forward to go faster and back to slow down.
This item allows MegaMan to jump much higher. The Jump Springs are vital in reaching many areas of the ruins.