What suggestions do you have for a National Guard MOS that makes for a good civilian job?

It's all relative to your local area, available civilian jobs and also what is available at units within a reasonable commute of your location. Without more information I have no idea what civilian and guard mos's overlap in your area. If you are trying to overlap like that you will need to do some research

Many employers are happy to hire a veteran if they display the work ethic that the military is known for.
However, 25B, 17 series and 68 series do offer specific training, certifications and/or credentials that are applicable to the their civilian counterpart jobs.

The medical field. You can go as far as you are up to

Naturally it requires a variety of factors to acquire civilian employment but these few are normally good on the outside:
1. medical maintenance 2. Xray technician 3.dental lab technician 4. Pharmacy technician. These 4 have usually been able to transition to the outside.

Medic, anything in technology/communications. These will not only give you a pretty good footing in the job market but will also be worth quite a few college credits.

51C Contracting

My experience in private and public management says experience in support MOS is often attractive to civilian employers. Logistic areas such as transportation, supply, maintenance (aircraft, vehicle, engine), civil engineering, medical (EMT, combat medic, corpsman), and contracting have direct application to similar civilian jobs. Information technology MOS have direct transferability to similar jobs in civilian industry. In IT it's often certifications that count more than education.

As others have pointed out in this discussion, attitude, integrity, and work ethic engendered by military experience are attractive to employers.

On the Engineering side, heavy equipment operators and tractor trailer qualified drivers translate into civilian employment, the Prime Power guys can usually hook up with the power companies also.

Signal jobs translate well enough.
Mechanic jobs don't translate as well, buy can help get you in the door somewhere. There is a huge jump in technology and troubleshooting with the automotive side, tractor/trailers a little less of a jump, and heavy equipment is probably the most similar.
Admin jobs transfer very well.
Truck driver is probably the easiest to transfer over.

....do your patrons a favor and don't be a cook.

What do you want to do?