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.

michielve

There are other good syntax highlighter plugins, but I wanted something simple and fast and 
be able to add the highlight classes with a select box in the TinyMCE editor.
I added some default languages: Javascript, PHP, Python, C, C#, VB.NET, SQL and CSS but you can 
easily add other ones.

Simple Fast Highlighter

Fast syntax highlighter written in Javascript.

Ion Snytax Highlighter vs Simple Fast Highlighter