I’ve got one! First, some context:

This is normal assignment unpacking:

    >>> a, b = 1, 2
    >>> [a, b]
    [1, 2]

(Mismatch gives errors)

    >>> a, b = [1]
    ValueError
    >>> a, b = [1, 2, 3]
    ValueError

Extra parentheses works too:

    >>> (a, b) = [2, 3]
    >>> [a, b]
    [2, 3]

Unpacking a single value:

    >>> (a,) = [4]
    >>> a
    4

Works without parentheses too:

    >>> a, = [5]
    >>> a
    5

No values does not work:

    >>> , = []
    SyntaxError

Neither does empty parentheses:

    >>> () = []
    SyntaxError

Now, the oddity:

    >>> [] = []
    >>> 

This raises no error! Neither does this:

    >>> [] = ()
    >>>