Fusion with MegaMenu
Fusion Menu is primarily a javascript enhanced CSS dropdown menu, that combines standard suckerfish type functionality with animations, transitions and other advanced effects provided by Mootools; in addition to other MegaMenu features such as multiple columns.
Versatile Splitmenu
Splitmenu is a static menu system that displays 1st level items in the main horizontal menu and all subsequent child menu items in the Sidebar. This location, and other parameters pertaining to SplitMenu, are configurable in the Gantry Menu widget settings.