Walk Through Walls
D004BED6 AE23
8004BED6 2400
D004BEEA AE23
8004BEEA 2400
D006CDA2 AE08
8006CDA2 2400
D006CDAA AE0A
8006CDAA 2400
D006D062 AE08
8006D062 2400
D006D06A AE0A
8006D06A 2400
D0078CEE AE23
80078CEE 2400
D0078D02 AE22
80078D02 2400
I tried hacking this sometime in late 1999/early 2000 and failed miserably. Now I know why.

There are a few slight issues with this code: It allows you to walk around the loading zones. So if you ever happen to find yourself in a part of the map that looks like half of the world exploded, you'll want to back-track on the proper path for a bit until you reach the loading zone. I have no idea where they are. you'll just have to look.
The other issue is that you might end up below the ground if you bypass an upward slope. It can be fixed with a "Moon Jump"-type code.