I really like "commando" from the old macintosh toolbox. It allowed you to create a simple GUI for a command-line tool, complete with checkboxes and text and numeric entries and menus. It showed you the actual command arguments as you selected options, and when you hovered over an option it explained what the option would do. Obviously a lot of tools need a more specialized GUI, but for a lot of simple or moderately complex tools that are used infrequently, it's great. Instead of looking up the man page, you just open the GUI and have the options explained to you while you configure the tool.