Unlock the secret weapons in the MegaMan X SNESgames

How does one obtain the secret weapons that can be unlock in the first 3 mega-man X on the SNES?

For instance:

• The Hadouken (MMX)
• The Shoryuken (MMX2)
• Zero's Sword (MMX3)

Solution 1:

I found an article here that will go into details with how to achieve The Hadouken and the Shoryuken.

Hadouken:

The Hadouken (波動拳 "Surge Fist") is a secret move Capcom included in Mega Man X and Maverick Hunter X. It is based on the Hadouken attack from the Street Fighter series, and is executed in the same way. In fact, in some versions of the game, X shouts the name of the attack, just like the Street Fighter series. While X's health gauge is full and he is on the ground, input the combination: ↓↘→+ATTACK. X should unleash a powerful energy ball. It is the most powerful attack from the game, causing 32 damage, being able to destroy most bosses and enemies in a single hit, with the exception of Mole Borer, Anglerge, Cruiziler, Utuboros, Thunder Slimer, RT-55J and Wolf Sigma. As the health of those enemies is above 32, they are killed with 2 hits, except for the Utuboros that takes 3 hits, and the Wolf Sigma who is immune to it. [...]

To obtain the Hadouken, obtain every Sub Tank, Life Up and Armor Parts. Play through Armored Armadillo's stage until the last rolling platform. As the platform bursts out of the tunnel and through the sky, dash-jump off of the platform and ascend the wall right on top of the gate to Armored Armadillo. There should be a Life Energy pellet. Depending on what console the game is played on, instructions will differ from this point:

[...] Collect the Life Energy item and restart the level (people usually jump into the large bottomless pit to restart at the halfway point rather than the beginning), and repeat until Dr. Light's capsule appears next to the pellet.

Shoryuken:

Shoryuken (昇龍拳 Shouryuuken, "Rising Dragon Fist") is the technique learned in Mega Man X2. Like the Hadouken, it is based on a Street Fighter attack, the Shoryuken. It is executed with →↓↘+ATTACK while X is at full health and on the ground. X will surround his arm with fire and perform a powerful uppercut, causing massive damage to its targets. While it is believed to kill all bosses in one hit, it does not. If the edge of the boss is grazed, it takes heavy damage, but does not kill it entirely. It is not saved in passwords.

In order to receive the Shoryuken capsule, X must own every other item in the game. The Shoryuken capsule can be found in Agile's station of the X-Hunters' fortress. After navigating the vertical passage with the jet platforms, let the Bat Bones follow him. Shoot one with the Crystal Hunter to reach the ladder. Ascend it to reach a spike-riddled challenge. It consists of a large sea of spikes, a safe area, and a [ shaped passage of spikes. To pass the first part, allow another Bat Bone to follow X. When X runs into it, use his invincibility to quickly cross the sea of spikes. The second part is more difficult: Either use an air-dash for one part of it and a charged-up Speed Burner for the other, or allow another bat to follow X and air-dash to cross the second part. Afterwards, have X slide down the left wall. X will drop into a corridor with the Shoryuken capsule inside, after getting an amusing message from Dr. Light: "Wow! You're so cool! I'm not worthy! I'm not worthy!."

In Mega Man X2 the Shoryuken can also be reached from the lower path by using the Crystal Hunter in the nearby Pararoid R-5.

This article also covers other secret items in the Mega Man X games that are obtainable by the light capsule.

As for the Z-Saber (Zero's sword):

Ultimate Armor, Z saber Ultimate Armor: Get to Doppler stage 1 with all heart tanks, sub tanks, robots, and upgrades (NO CHIPS). After you destroy the dinosaur robot on half-stage, continue to the place where the first spiked balls fall. Wall-slide the left wall and you'll reach a secret passage. You must have full health. The capsule you find will give you the effect of all four chips and color your armor gold! If you quit the game it doesn't save the gold armor.

Zero's Z saber You need to get to Doppler stage 2 with zero alive and Vile killed with spinning blades when you fought him at his factory. The level should be different then usual. When you get to near the door that the bug is in (above the water zone) switch to zero and let him pass the door and destroy the bug. When you destroy it, it will crush zero and there will be a cut scene showing that zero needs repairs. GIVE X THE Z SABER. Your fifth charge will now be green and after the cross charge you can shoot a long rang z saber attack that destroys every boss in two hits! (This one can be saved.)

Source for Zero's Saber.