If you have a WordPress blog, you definitely need the WP-Ban plugin!

Ban users by IP, IP Range, host name, user agent and referer url from visiting your WordPress’s blog. It will display a custom ban message when the banned IP, IP range, host name, user agent or referer url tries to visit you blog. You can also exclude certain IPs from being banned. There will be statistics recordered on how many times they attemp to visit your blog. It allows wildcard matching too.

We all get those annoying spam comments for credit reports, adipex reviews, acai trials and a hundred other things, and with WP-Ban you can just block the spammers and not have to worry about them returning to your blog! Also works great for people trying to start drama