RazielKanos

This plguin simply adds a CSS code into your Admin Dashboard and hides most of the nagging messages telling you 
that you should activate or register other GPL 2 Plugins.
It doesn’t add any functions other than adding the CSS code, so there should be no trouble with other plugins you are using.

WP Remove Admin Register Nag

This plugin removes the reminders that you should register plugins you got by a theme for example

joetan

A simple pre-filter to weed out the most obvious comment spam (about 90% of all spam).
Legitimate comments that get blocked (either by this plugin or by Akismet) can be presented with a captcha to confirm that the comment is legitimate. Comments that don’t pass the captcha will be immediately discarded.
Helps you identify potential spam words (you can use this to tweak the plugin’s filters).

TanTanNoodles Simple Spam Filter

A plugin that does a simple sanity check to stop really obvious comment spam before it is processed.

WP Remove Admin Register Nag vs TanTanNoodles Simple Spam Filter