John

This plugin enables you to highlight syntax using the PEAR Text_Highlighter class. Other syntax highlighters that use GeSHi have slower rendering speeds which will increase your page load time. However, this plugin gives you the speed and efficiency provided by the PEAR developers. You even have the option of enabling or disabling the line numbers as well as specifying your own style.

Ion Snytax Highlighter

This plugin allows users to highlight code.

garethgillman

This plugin prettifies/beautifies/highlights source code placed inside <code><pre class="prettyprint"></code> tags. It is a light plugin with only 2 files.
New in 3.2.2 – use the hammer icon in the editor to paste your code and automatically have it converted to pretty code.

Syntax Highlighter Lite

This plugin prettifies/beautifies/highlights source code placed inside `` tags. It is a light plugin with only 2 files.

Ion Snytax Highlighter vs Syntax Highlighter Lite