If you could pick only 4 symbols to use in combination with the 26 letters of the English alphabet, what would you pick and why?

The picked symbols should functionally enhance or compliment the 26 characters of the English alphabet. There is no restriction on the 4 chosen symbols, so go wild.

An example of an acceptable but not ideal response:

.  (period)  Useful for separating words into sentences.
@  (at sign)  Used in email addresses.
?  (question mark)  Indicates a question is being asked.
ಠ  (kannada eyeball) Needed for looks of disapproval.