Diana K. Cury

Very simple pluing, no configs, no screens, just action! 
Simple Smilies add all WordPress smillies in comments form and a simple javascript let users click them to insert. 
This is a very light plugin, the javascript only loads when in singular/single contexts, also there is no stylesheets.

Simple Smilies

Let users insert WordPress smilies when commenting in you site.

Jeff Waugh

Replace the blocky default (GIF) smilies with beautiful Tango/GNOME (PNG) smilies.
If you want to use this plugin with a version of WordPress prior to 2.8, please use version 2.0.

Tango/GNOME Smilies

Replace the blocky default (GIF) smilies with beautiful Tango/GNOME (PNG) smilies.

Simple Smilies vs Tango/GNOME Smilies