[jbaviat]

Nice.

What first revealed me the hidden complexity of SSH was typing this during a live SSH session:

    ~?

Which show you the SSH supported escape sequences.

[jjnoakes]

Note that the actual sequence is 3 characters (newline, tilde, question mark). If you try ~? after anything except a newline, ssh won't intercept it (this is true for all ssh tilde escapes).

Telnet had something similar.

[arantius]

This is of course specifically how to reveal these features in the OpenSSH client. If you're using another client (e.g. PuTTY) there's a different way to get to these features (click the menu).