Shapes

Shape examples: 
        graph TD;
            sq[Square shape]-->ci((Circle shape));
            od>Odd shape]---|Two line <br>edge comment|ro;
            od2>Really long text in an Odd shape]-->od3>Really long text with linebreak <br>in an Odd shape];
            di{Diamond is  <br> broken}-->ro(Rounded <br>square <br>shape);
            di-->ro2(Rounded square shape);
            e((Inner circle))-->f(,.?!+-*ز);
            style e red;
graph TD; sq[Square shape]-->ci((Circle shape)); od>Odd shape]---|Two line
edge comment|ro; od2>Really long text in an Odd shape]-->od3>Really long text with linebreak
in an Odd shape]; di{Diamond is
broken}-->ro(Rounded
square
shape); di-->ro2(Rounded square shape); e((Inner circle))-->f(,.?!+-*ز); cyr[Cyrillic]-->cyr2((Circle shape Начало)); style e red;

Sequence diagrams (experimental)

        sequenceDiagram
        Alice->Bob: Hello Bob, how are you?
        Note right of Bob: Bob thinks
        Bob-->Alice: I am good thanks!
        Bob-->John the Long: How about you John?
        Bob-->Alice: Checking with John...
        Alice->John the Long: Yes... John, how are you?
        John the Long-->Alice: Better then you!
sequenceDiagram Alice->Bob: Hello Bob, how are you? Note right of Bob: Bob thinks Bob-->Alice: I am good thanks! Bob-->John the Long: How about you John? Bob-->Alice: Checking with John... Alice->John the Long: Yes... John, how are you? John the Long-->Alice: Better then you! 
    graph TD;
        sq[Square shape]-->ci((Circle shape Начало));

Dot syntax (experimental)

        digraph
        {
        a -> b -> c -- d -> e;
        a -- e;
        }
digraph { a -> b -> c -- d -> e; a -- e; }