\t is your best shot. For good measure, you'll also want to add double quotes (can be used to escape commas in CSVs), double double quotes, back slashes, and |s, just to mess with anyone trying to sanitize a CSV with your password in it.
Of course. In Windows you can hold Alt and type 0 0 9 before releasing the Alt key to enter the character without triggering any "move to next field" behaviour. In *nix it should be Ctrl+I.
Similar with other control characters - NUL (0) might be harder to type, yet substantially more likely to break things!
SHY is good if you'd like a character which can't be seen, without needing to resort to Unicode.