This is what I've confirmed can be done on an Android phone. (From what I've read, Apple is superior in its speech-recognition of punctuation.)

Result Command
Enter once then capitalize "new line"
Enter twice then capitlize "new paragraph"
. "period" "dot"
? "question mark"
! "exclamation point" "exclamation mark"
, "comma"
- "hyphen" "dash"
% "percent sign"
:-) "smiley face"
:-( "sad face"
... "dot dot dot"