Wordfence - Comprehensive security plugin for WordPress.
Shield Security - The most advanced and easy-to-use WordPress security plugin.
iThemes Security - Security plugin that provides over 30+ ways to secure and protect your WordPress site.
Sucuri - Website Protection, Malware Removal, and Blacklist Prevention
Defender - Encompassing security solution for WordPress.
NinjaFirewall (WP Edition) - A true Web Application Firewall to secure and protect WordPress.