Gesundheit

[Becky]

German, meaning health. Used to wish someone health after sneezing. It has been exported, but seems primarily to be used in the US. Similar is [bless you]

[Sarah]

Used as a reply in certain contexts when someone has just said something quite verbose or confusing. Bless you can be used in the same way in this sense. Not all native speakers of English use it.

[Becky]

Reflex response to a person who has just [sneezed].

[PussyCat]

Means stop sneezing in German. During the Middle Ages, it was thought the Black Plague was spread through sneezing, therefore stop sneezing, or Gesundheit was frequently heard.