First, go to ProtoMan's room in CloudMan's stage (right before the outdoor part before the boss, there will be a ladder. Use Rush to get to it). ProtoMan will comment about using weapons to find areas. Then go to ProtoMan's room in TurboMan's stage (this one is at the very top of the area with the traffic light platforms; go through the wall just before you reach the top of the ladder). He will mention something about the Super Adaptor.
After you go to these two rooms (doesn't matter with order you go to those), go to ShadeMan's stage. Continue like normal until you reach the Pumpkin mini-boss. Shoot the small orange core of the Pumpkin (NOT the eyes on the outside). After you defeat it, it will open a hole on the bottom. Go down until you reach the room with a lone green Sniper Joe. Defeat the Sniper Joe, and instead of going down the ladder, go right through a secret passage and enter the gate you find. If you did everything correctly, ProtoMan will challenge you to a duel.
Once you defeat ProtoMan, he will give you the ProtoShield. This can be used at the same time as the MegaBuster (don't forget to select it), and it will block many enemy shots (like those birds that hatch from the egg; let all of them run into the shield and they will die).
Instead of holding the B button as you would in the SNES version of MM7, simply hold the Square button and select his level for his alternate stage music. This will not work if you have beaten Shade Man already.
All of these passwords will allow you to access all eight of the stages at the very beginning of the game instead of only the initial four, with a few other effects. The downside is that the Museum stage will be skipped, and the game will give you invalid passwords until BurstMan, CloudMan, JunkMan, and FreezeMan are defeated.
Go to the weapon menu and select the Pharaoh Shot weapon. While holding the square button, leave the menu. The weapon will start charging up (you'll see a ball over your head), but will not use any energy.
Once it's fully charged, you can ram the ball into an enemy. The moment you hit an enemy with it, press Start. If timed correctly, the Pharaoh Shot's energy will not have decreased. You can now do this trick again if you want to.
You need the Flame Sword power before you do this First find an area with a vampire bat and equip the Flame Sword. Let the bat dive at you and right when the bat latches onto you use the Flame Sword. If done correctly you should see a silhouette of megaman's head behind him and every time you move a “box” of silhouettes will appear in front of you. Every time something touches these silhouettes it damages them. Note: This glitch is cancelled if you are hit or use the Flame Sword again.
In Mega Man 1, when using a weapon that goes through an enemy --- Rolling Cutter, Thunder Beam, Ice Slasher, or Fire Storm --- press Select the second the weapon hits an enemy. After you press Select again to unpause the game, the weapon will hit the enemy a second time. This makes a joke of virtually every robot master battle in the game, so long as you have a weapon that can be used in conjunction with the glitch.
Unfortunately, this was fixed in later versions of Mega Man, and does not work in any other title besides Mega Man 1.
When playing Mega Man2 select a boss with the X button and continue holding the X button and instead of seeing stars in the background you will see little red birds flying around in the boss introduction.