I'm Magento Developer. The past 3 years I have worked in this area.
Good knowledge of: OOP, PHP5, MySQL, HTML, CSS, JavaScript, Prototype Js, GIT.
Also familiar with jQuery, Varnish Cache, Phing, PHPUnit.
Good knowledge of Magento, including: high-level architecture of the platform, structure of a typical module, structure of typical design theme, config, request workflow, core classes, etc.