Because reading about Ion Storm's original FPS/RPG masterpiece never gets old, you should proceed over to Itchy Thumbs for the latest Deus Ex retrospective to grace the Internet.
RPG qualities in the game include a large set of skills that can be levelled up through experience, upgradable weapons with various forms of ammunition and nanotech augmentations that provide various powers such as a cloaking field or regenerating health. The skill upgrades offer very tangible improvements for player character JC Denton's abilities. For example, at the start of the game the aiming reticule for most weapons is large, representing the possible area within which bullets will hit when fired. Upgrading skills with each weapon will shrink the reticule and tighten your aim. Depending on what skills you improve, JC Denton can approach different challenges in various ways and the game is designed to ensure that these choices arise often.
On top of these character upgrades the game features extensive dialogue options that not only shift your allegiances throughout the story but determine the fate of key characters. All of this coupled with three possible endings adds up to an impressively malleable narrative. The story itself is steeped in government conspiracy and intrigue, featuring some grim and sometimes oddly prescient suggestions at the direction of the 21st century.