The "Prayer" discussion started by Vitomama made me think of this. What do you say when someone sneezes?
I have always said, "bless you" because it is polite, but I feel slightly odd saying it. Recently I started saying, "gesundheit" which is really just wishing someone good health, but I feel odd saying this, too as I am not German. I believe both became a custom during the 14th century because one of the symptoms of the bubonic plague was sneezing, so they are probably a little out of date, but I feel it is rude if I don't say anything.