lx6g

You can choose from upper and lower letters, digits and special characters to make your new hardcore passwords impossible to break. 
And yes, all the passwords are generated only within client’s browser session and are not saved anywhere on the server side, 
so it is absolutely safe to use in real world.
You can also specify the following attributes to tune the form’s appearance:
<ul>
<li><code>length=4..64</code> specifies the default length of a password. Allowed values range from 4 to 64. </li>
<li><code>upper=1</code> enables upper-case letters option. Activated by default.</li>
<li><code>lower=1</code> enables lower-case letters option. Activated by default.</li>
<li><code>digits=1</code> enables digits option. Activated by default.</li>
<li><code>special=1</code> enables special characters <code>,.:;_=</code> option. Disabled by default. </li>
</ul>
Plugin’s Official Site
<a href="http://lx6g.com" rel="nofollow ugc">Alex Granovsky Blog</a>

LX Password Generator

LX Password Generator is simple yet nifty password generation form to be placed in any page or post you like.

oakcreekdev

Secure Password Generator is a plugin written by Oak Creek Development that allows you to add a secure password generator to your WordPress website. Just place the shortcode: [secure_pw_gen][/secure_pw_gen] on any page.
This can be a great way to encourage your users within your organization to start using secure random passwords for everything. It is easy and convenient to keep a pinned tab open on your public or internal website.

Secure Password Generator

Adds a secure password generator to your WordPress website.

LX Password Generator vs Secure Password Generator