Unless there is a requirement for a fire rating or some other assembly. SFR's using TJI's will often be required to use 5/8" type X drwall because engineered lumber burns much more rapidly than nominal sawn lumber. Some areas have recognized the use of fire rated 1/2" GWB, but this is not universal1/2" is acceptable on ceilings if framing is 16" o.c., 5/8" for 24" o.c. framing.....
Just for reference, I used 3/8 on my garage walls, and it seems strong enough. I know...lots of people don't recommend it, but it worked, it's lighter, and cheaper, and it was just my garage.
It has been a while since I hung drywall, but I am pretty sure that the house/garage wall must be hung with firecode drywall. I seem to recall doing that every time.3/8" should not be used period. It is made for specific purposes as I stated above.
New houses here are built with 1/2" regular drywall.
5/8" or 1/2" Fireguard is not required, nor does it make the garage "Fireproof".
Fireguard, Type C or Type X... all it means is that it has a rating, a set of properties. It simply performs a certain way at a certain temperature for a certain amount of time.
Even 1/2" regular will "protect" against fire to a certain degree.