Python - what are all the built-in decorators?

They're not built-in, but this library of example decorators is very good.

As Abgan says, the built-in function list is probably the best place to look. Although, since decorators can also be implemented as classes, it's not guaranteed to be comprehensive.

I don't think so. Decorators don't differ from ordinary functions, you only call them in a fancier way.

For finding all of them try searching Built-in functions list, because as you can see in Python glossary the decorator syntax is just a syntactic sugar, as the following two definitions create equal functions (copied this example from glossary):

def f(...):
    ...
f = staticmethod(f)

@staticmethod
def f(...):

So any built-in function that returns another function can be used as a decorator. Question is - does it make sense to use it that way? :-)

functools module contains some functions that can be used as decorators, but they aren't built-ins you asked for.

Decorators aren't even required to return a function. I've used @atexit.register before.