Formal:
* Autograph: This is the most common term for a signature, especially when it's considered valuable or collectible.
* Signature: You can simply call it a signature, but it should be clear from the context that it's a famous one.
Informal:
* John Hancock: This is a playful term, referring to the large, bold signature of John Hancock, one of the signatories of the Declaration of Independence.
* Scribble: This is more informal and might be used in a humorous way, but it's not always appropriate.
Other options:
* Iconic signature: This emphasizes the distinctive and recognizable nature of the signature.
* Signature mark: This is a more general term that can apply to any recognizable mark, including signatures.
Ultimately, the best term to use depends on the specific situation and the level of formality.