A project made for IMBCraft to give a player a GUI container to select a "class" on join, which is configurable to be unchangeable afterwards. This plugin is configurable through a generated config.yml file, so there's no need to edit the code.
CyberFlameGO/RankPicker
A plugin which gives a GUI on join (unless you have a permission to "bypass" it) which executes certain commands (as console) when a material (defined in the configuration file) is selected.
JavaGPL-3.0