I've been at my current employer for going on 8 years and pretty early on it was apparent that when people sneezed here, most of the time no one said "god bless you" or "bless you" or anything really. I don't say anything myself, because I'm not a "Believer" and I think Gesundheit is something only German people should say when someone sneezes, or at all if truth be told, because most people don't say it right anyway, so it just comes across as uneducated. My wife says "bless you" because she's still got a little Catholic in her (insert joke about things being in my wife here), but I've mostly beaten the religion out of her as well (figuratively speaking of course). My son was pretty much just raised knowing there's organized religion and "daddy thinks those people are crazy, but as long as they leave him alone, more power to them". My wife thinks that even though she's mostly sure there's no "god" per say, there's merit to having your children raised by religious guidelines, that it's important to have those sort of rule sets in place to keep them on the right path. I just remember banging this girl from church when we were both 15 who got dragged to church by her parents but didn't believe in any of it either and had sex just to get back at them for making her go.
So, if you don't believe in a god that would somehow have direct control over the life of those around you based on whether or not they might sneeze, do you still say something in response when they do?