Passwords Not Needed
Clicking on these links will take you to the launch page of the respective episode, so you won't have to worry about passwords at all. These links might not work forever.
Episode 2: The Black Isle
Episode 3: The Ancient City
Episode 4: The Lair
Episode 5: Waken Awaits
Note: Some people reported having problems closing the FireChild window after using these links. I tried it and there's a simple solution. To close the window you just switch to AOL using Alt+Tab and click yes on the prompt that asks you, "Do you want to close the Window?"

 
Climb Walls
     I haven't tried this in episodes 1+2, so just follow along on episode 3. In the very first area, after passing under the first tall bridge, there should be a dead-end trail on your left. Go to the very end of the trail, as far as you can run. You should have a wall on your right and a very long drop on your right. Keep Lona running into the wall, she should be running in place. Now start alternating between the jump button (space bar) and holding the forward button. Lona should get "locked" in place in midair and continue to get locked higher and higher if you keep going. Usually when I do it, I tap the space and forward buttons back and forth, so I make Lona kind of "climb" the walls. You can do this in a lot of places in episode 3. Corners usually work best, but some walls are climbable.
     It helps if you look straight up or down while doing this, and you can substitute the back arrow if you put your back to the wall. In other words, you can climb a wall backwards by using the back button instead of the front. Now what's the use of climbing up walls if there's no prize at the top? Well there are some practical uses:

1. If you were succesful in climbing over that dead-end, you should have arrived on the top of that wall, which is no special place, it's just a ledge. However, you will find that the wall directly in front of that ledge is climbable. If you start climbing that wall you will eventually bump your head on an annoying ledge sticking out of the roof. Well if you were able to lock yourself in place near the top, you can actually jump away from the building then change direction in midair towards the building. By doing this, you will literaly jump to the side and over that obstacle. Now you are on the roof; this is an area you are not supposed to be in yet, so you beat the system, you stuck it to The Man! ...Anyway, you can do this in many places and skip fights, cutscenes, and puzzles. There's one downside: you can't get very far in the game without triggering those sequences, so you're eventually going to have to go back and trigger them. 2. You can also gain acces to "The Abyss" using this method. There is an invisble barrier keeping you from falling off the edge of the cliffs at all times. In the area where the Meroo cutscene is activated, in the place where the game takes over, there should be an invisible barrier to you left. Most of these barriers are flat, but this one seems to contain a corner. Peform a wall climb backwards, facing away from the barrier and looking down. This way you should be able to see yourself climb up thin air. Eventualy this invisible corner ends, because the programmers didn't expect anyone to get this high up. This is not a good thing. If you manage to get over the barrier and you will start falling. If you don't land on the floor you will fall into The Abyss. There is no escape from The Abyss, so use this cheat wisely. Enjoy.

 
The Abyss Behind The Doors
In FireChild, stepping on the area directly behind a doorway triggers the game to take you to the next room, but you can bypass this trigger by jumping over the "hotspot" on the floor. Jump as far as you can into the next room without touching its floor. You should be in a corridor that ends in darkness. Don't walk toward the darkness unless you want to fall into an endless abyss.

 
Rapid-fire Weapons
      Wow, I'm surprised I found all these cheats by just playing, but this one is pretty cool. Hold down the 1 button (number one) on your keyboard and shoot away. Notice the shots look and sound different. When you switch to the fury laucher, it only lets you shoot at a slow rate. Ok, now here's the good stuff. Hold down 2 and start shooting; you will be able to shoot the second weapon about twice as fast. You should do this with a blue fury fountain nearby because this really drains your blue meter. Now, Rapidly tap 2 and fire as fast as you can. You will be shooting at about four times the normal rate.
      Do the same thing for the primary weapon. Tap 1 and fire at the same time as fast as possible. After a few seconds, you will be shooting charged shots at an incredible rate. This doesn't drain your blue meter like the secondary weapon and it's much faster.
      So how do you put this to use? Since it's pretty hard to move around while doing this cheat, your only options are to stand still. Maybe you could turn on the NUMLOCK option on your keyboard to lock the numberpad into number mode.