Anyways, this modding tool is called Liberty.
Liberty is an open-source Halo Reach modding tool.
This tool enables you to mod so much more with your campaign, such as health, ammo, what you want, when, where you start, where THEY start. And much more.
This tool is pretty smart in my opinion, as for those which aren't that 'great' at modding, this does all of it for you.
It's simple to use and gives an array of options.
You will need a USB stick though.
Download Link:

Virustotal:

I take no credit in making this, though I can answer questions about it if you need help.
I will add screen shots soon if anybody is interested.
If this is in the wrong section, just tell me. Thanks.