Mega Man X4/Items

Web Spider
Requirements: Rising Fire when playing as X, Ryuenjin (learnt from defeating Magma Dragoon) when playing as Zero

Get Rising Fire if playing as X or Ryuenjin if playing as Zero. In Area 2 of the stage, there multiple trees which have parts that can be burned with these moves. Stand under the second tree, beneath the electric web enemy, and use Rising Fire or Ryuenjin to reveal a Heart Tank for the taking.

Split Mushroom
Requirements: None, Lightning Web when playing as X or Kuuenbu (learnt from Split Mushroom) when playing as Zero may help

The Heart Tank sits out in the open, above the beginning of the main path of the level section just after the giant staircase in Area 2. Run forward a little, and the level will start to collapse where you were standing. Wait for the platform to fall a little, then wall jump up on top of the platform. Stand to the left of the crusher enemy and wait for it to fall. Once it has fallen, quickly jump up and wall jump up to the Heart Tank. If you are playing as X and fail this, you can shoot Lightning Web from the ground level and dash jump off the web up to it. If you are playing as Zero and fail it, you can use the Kuuenbu's double jump, but this will require revisiting the stage, it may be more practical to suicide down the pit and try again; there is a checkpoint right at the Heart Tank's location.

Cyber Peacock
Requirements: None, Soul Body if playing as X or Kuuenbu (learnt from defeating Split Mushroom) if playing as Zero recommended

When playing as X, complete the first speed section to an 'S' ranking to find the Heart Tank sitting in front of you in the next room. When playing as Zero, you have to complete the second speed section to an 'S' ranking; the first will only yield a life. Remember that Soul Body/Kuuenbu can eliminate the pesky yellow electric balls which try to slow you down.

Storm Owl
Requirements: None

In Area 1, a little beyond where you fine the stage's Ride Armor, the Heart Tank sits out in the open on the platform. However, if you don't pick it up fast enough, a giant laser from above will destroy the platform and cause the Heart Tank to fall into the pit. It may be easier to get the Heart Tank in time if you abandon the Ride Armor before getting there. The only ways to bring it back are suicide or a stage revisit.

Magma Dragoon
Requirements: None, Lightning Web when playing as X or Kuuenbu (learnt from defeating Split Mushroom) when playing as Zero recommended

The Heart Tank is located on a ledge back to the left as you encounter the first enemy in a Ride Armor in Area 2 of the stage. With a precise dash jump off the wall below the ledge, it is possible to grab the ledge and obtain the Heart Tank without any items. This may take a few attempts however. If you are playing as X, you can alternatively use the Lightning Web from the opposite ledge for an easier time making it there. The double jump learnt from Zero's Kuuenbu move may also make it much easier getting to the Heart Tank.

Frost Walrus
Requirements: Rising Fire when playing as X, Ryuenjin (learnt from defeating Magma Dragoon) when playing as Zero

From the beginning of Area 1, take the lower route until the first instance of reappearing, disappearing platforms. Pass the first platform, but before passing the second platform, jump up, and you should see the Heart Tank sitting on an ice platform above your head. Use Rising Fire if playing as X, or Ryuenjin if playing as Zero, to break the ice and claim your reward.

Jet Stingray
Requirements: None

In Area 1, don't jump when you come to the third gap. You will fall down to the lower platform and run straight into the Heart Tank. Remember to jump after getting it though, otherwise you will plummet to your doom in the next gap.

Slash Beast
Requirements: None

Erm... the Heart Tank sits right out in the open a little after your first encounter with the stage's Ride Armor. It's not even hidden or requires any sort of item or special movement to get to. Did you really need to read this guide for it? For shame.

Sub Tank 1
Function: When you pick up health while X is already at full health, it will fill up these health Sub Tanks. Use them any time to increase your health; handy in boss battles.

Location: Cyber Peacock's stage

Requirements: none; Soul Body if playing as X or Kuuenbu (learnt from defeating Split Mushroom) if playing as Zero recommended

Obtain an 'S' ranking in the second speed section of the stage to find the Sub Tank sitting in front of you in the next room. If you are playing as Zero, you must obtain an 'S' ranking in the third speed section. Remember that the Soul Body/Kuuenbu can eliminate the pesky yellow electric balls that slow you down.

Sub Tank 2
Function: When you pick up health while X is already at full health, it will fill up these health Sub Tanks. Use them any time to increase your health; handy in boss battles.

Location: Jet Stingray's stage

Requirements: none

Near the end of area 2, just after your second encounter with Jet Stingray flying in the air, jump off the last ramp onto a platform, then tap the jump button (don't jump too high), and finally dash. You should fly onto a high platform and gain a Sub Tank. If you dash too high, you will go flying over the Sub Tank and either have to suicide or revisit the stage for it.

Weapon Sub Tank
Function: Works identically to the health Sub Tanks, except for weapon energy instead of health.

Location: Frost Walrus' stage

Requirements: none

It is located frozen in one of the last blocks of ice in area 2 before moving onto the part of the stage with the birds who freeze everything over. If you follow the lowest route possible through the ice block section, climb the vertical shaft with some Mets off to the side, then back track to the previous blocks of ice, you should see the Weapon Sub Tank. Simply destroy the ice and grab it. Because of the chaos of all the enemies proceeding it if you take the other route through the ice leading to it, it is quite easy to pick up the Weapon Tank accidentally.

EX (Life) Tank
Function: Technically not a Sub Tank in the traditional sense, once you obtain it, whenever you load a saved game or game over on a stage, you will restart that level with four lives spare instead of the standard two lives.

Location: Frost Walrus' stage

Requirements: Lightning Web if playing as X, Kuuenbu (learnt from defeating Split Mushroom) if playing as Zero

It is located up a wall at the end of the slippery slopes of ice in area 1. Initially, you are going down these slops to the right, but then double back and go down and to the left. Before going down there, climb up the wall to the right. You will see the EX Tank sitting on a ledge with an overhang above you. If playing as X, shoot a Lightning Web off the wall, dash jump off the wall onto it, then dash jump off the web onto the ledge to collect the EX Tank. This may take a few tries. If playing a Zero, use the Kuuenbu's double jump function to reach the edge of the overhang and climb up to claim your item.

Interestingly, both of the game's unique items (the Weapon Sub Tank and EX Tank) are located in Frost Walrus' stage. This makes Walrus' stage the only one in the game with three items/upgrades to collect even if you are playing as Zero. This also makes it the only stage in the series up to this point with two Sub Tanks. Throw in the fact that the stage features both cameos from Blizzard Buffalo at the very beginning and Chill Penguin in the miniboss room, not to mention two stage themes for each half of the stage (a first for the series up to this point), and Frost Walrus is a really unique stage.

X's armor upgrades
The four upgrades are sorted here according to the game progression suggested in the guide. The upgrades can only be utilized by X, Zero cannot.

Leg Upgrade
Location: Web Spider's stage Requirements: None

The boots upgrade is found near the beginning of Area 1 in a cave hidden behind a waterfall on the right wall. This gives you the ability to hover for a short time by pressing the jump button while in midair. You can move backwards and forwards when hovering, but this will decrease your hover time. It also allows you to air dash.

Head Upgrade
Location: Cyber Peacock's stage Requirements: None, Soul Body recommended

Achieve an 'S' ranking in the third speed section to get it in the next room. Remember that Soul Body can eliminate the pesky yellow electric balls that slow you down. With this, special weapons won't consume any weapon energy unless they are charged.

Arms Upgrades
Location: Storm Owl's stage Requirements: Lightning Web

Notably, there are actually two arm upgrades in this game. You can't equip both at the same time, so you have to pick one. However, you can always go back to the capsules to switch to the other one later. They are both found in Storm Owl's stage, above the spike-lined area. Fire a Lightning Web from the right platform onto the left wall of the spike shaft, then dash jump and wall jump off the web up to the capsules. This may take a few tries and deaths. The second capsule is just beyond the first to the left.

Both upgrades enable X to charge special weapons.

The first capsule you'll find contains the Stock Charge upgrade. This enables X to charge up to four charged shots at once, and then fire them one after another. Note that the shots are not fired when you release the fire button: that just makes you stop charging; you must tap the fire button again to start firing them.
 * Stock Charge

Right behind the Stock Charge capsule is the second capsule containing the Plasma Shot upgrade. This gives X a bigger, much more powerful fully-charged shot that leaves behind a plasma ball on impact, which does further damage to any enemy that touches it.
 * Plasma Shot

Body Upgrade
Location: Magma Dragoon's stage Requirements: One of the two Arm Upgrades & Twin Slasher

When you first encounter the Ride Armor in Area 2, dash jump off the initial ledge you find it on, then jump out of the armor to grab the ledge close to the ceiling. Climb up here and use a charged Twin Slasher to break open the rocks blocking the way to the capsule. This enables X's Nova Strike Giga Attack, an extremely powerful air dash attack. It needs full weapon energy to work, but it can recover energy either from weapon energy capsules or from damage X takes. It also reduces damage inflicted to X, much as the same as the previous three games in the series.

Ultimate Armor
This armor can only be obtained with a cheat code. On the character select screen, highlight X, and press twice,  six times, then hold  and  and press.

X will now be colored blue and purple when the game starts. Now, any upgrade capsule will grant X the Ultimate Armor. It's got the same capabilities as the normal armor upgrades (including the Plasma Shot buster upgrade), except it allows unlimited use of the Nova Strike, and you get it all at once instead of in pieces.

Black Zero
If playing as Zero, you can obtain his black armor through a cheat code. Highlight Zero on the character select screen, then hold, press six times, release , press and hold  (hold this until the level starts) and press.