Nimbus Digital

Redirects http://somedomain.tld to http://someotherdomain.tld
Assuming you have 2 or more domains in use for a single WordPress site. This plugin forces the use of only one no matter which is entered in the address bar.
If, for some reason, your host won’t automatically redirect from one domain to another, then this plugin will do it. It checks the URL used to access the site and does a 301 redirect if incorrect.
In theory htaccess should do this, but in my case it didn’t. Perhaps because I am using domain aliases (or CNAMEs) and I wanted to insure that the main one was always in use, even when accessed using old links.

Force Domain Redirect

Forces your Wordpress site to load on the domain registered in the WP admin.

devoutpro

NoMore404 is a free WordPress plugin for redirection of 404 pages and simple firewall to block malicious hosts and URLs. 
All redirections are done via 301 redirection. 
You can mark any hosts and URLs to be blocked as malicious as well.

Nomore404 404 Redirection and Firewall

NoMore404 is a free WordPress plugin for redirection of 404 pages and simple firewall to block malicious hosts and URLs.

Force Domain Redirect vs Nomore404 404 Redirection and Firewall