Which is interesting, since the formal name for the Mormon religion is "The Church Of Jesus Christ Of Latter Day Saints".

Do they have their own personal jesus?

Yup. And a ladder of de saints.

It's very rare outside of a church/ Christian group.

I don't hear it here either.

Strange. What about when people sneeze?

Gesunheit/Bless You are about equal here, but never God Bless

I say "Blow your nose, snot head!" :D

"Bless you" here.

Never Gesundheit; although many adults would recognise that from American TV/ films/ books it would be seen as pretentious. Like saying gasoline instead of petrol.

Was fairly common among my family/social group. Maybe I'm pretentious?

Must be regional then.
I have honestly only heard it once. And that guy was a pretentious prick.
So that might have coloured my view.

The only people I've known who say Gesundheit were deliberately choosing it as an atheist alternative to "bless you."

Now they've taken to ending phone calls with "Have a gesundheited day!"

:D

Have a Noodly Day.

Yes, that's why I use it, but it was around plenty for me to see it as a reasonable option.