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.

arunpyasi

Astranix Technologies Pvt. Ltd.

sushilsubedi32

WordPress Strong Password Generator is a plugin for WordPress to generate strong passwords of length 6 to 256. You can choose to include capital letters, small letters, number and special characters in the password. This plugin also allows the generated password to be copied to the clipboard.
<h4>Major Features</h4>
<ul>
<li>Add widget with shortcode anywhere in the site.</li>
<li>Easy to use widgets available.</li>
<li>Visitor can choose to include small letters, capital letters, numbers and special characters in password.</li>
<li>Password Length can be chosen.</li>
</ul>

WP Strong Password Generator

WordPress Strong Password Generator is a plugin for WordPress to generate strong and random passwords.

LX Password Generator vs WP Strong Password Generator