Extra Sub-tank
Earn an extra sub-tank that refills Mega Man X's life meter by exploiting a glitch. Find three of these devices, then select a special weapon -- which you get by beating the Reploids -- that does not have full power. Grab a weapon capsule that refills the special weapon's power and quickly hit "Start." If you do this fast enough, you will get a fourth sub-tank.
Bosses Beaten Cheat
From the game's main menu select the option to enter passwords. Use the cheat code "3676 4667 5148," starting with the top row left to right and finishing at the bottom. This code will give you all the armor upgrades and power-ups and will take you to the final series of stages in the game.
Subtank Cheat
Go to the password screen and enter "5724 8418 3588." This code nets you all four of the life-filling subtanks. You will not have the other upgrades and will still have to beat the bosses in each level.
Shooting Fireballs
First, earn all of the game's power-ups, then head to the Armored Armadillo stage. When the last mine cart launches into the air, jump to the wall and climb up it. Grab the energy unit at the top and then die on purpose by jumping into the pit. Repeat this process four times. The fifth time you reach this ledge, you will get a fireball for your blaster, much like the one Ryu shoots in the other Capcom game series, "Street Fighter."