The keystrokes of Shift/Option/9 on a Mac keyboard will enter a decimal point as distinct from a period. This is useful when entering payment amounts into calendar apps such as BusyCal & Fantastical which accept normal English entry. Because, if I enter a dollar amount using a period, the app will recognise the first number as a date, which is clearly undesirable. Using a decimal point fixes this issue.
I find it so handy that I’ve reallocated the Command/Comma keystroke combination to enter this symbol ·