How does a procedurally-generated action-RPG that can be played during a lunch break sound to you? Ruins of Endoth [official site] might be a typical dungeon crawling roguelike in a generic fantasy setting, but it designed to be action-packed and all over within 45 minutes.
You'll get your randomly-named character with his or her random stats, loot some equally randomly-placed corpses for some random equipment and enter the semi-random dungeon to kill and be killed.
Everything extraneous about the genre has been sliced away, and the combat, inventory and leveling are handled simply and elegantly enough to ensure you'll have grasped the mechanics of Ruins of Endoth within the first five minutes of loading the thing. After a couple of perma-deaths, you'll also be experienced enough to progress to the dungeon's deeper levels and appreciate the variety of loot and monsters.
Ruins of Endoth may be a game designed for short sessions of play, but it's also one that took a year to develop and the time and love poured into it shows despite the odd bug. Chances are it will become your casual RPG of choice; perfect while pretending to work.
If that sounds appealing, Ruins of Endoth is available for £2.99 on Desura, and is also singing for its supper on Steam Greenlight, though frankly all seems to have been pretty quiet since last Summer (when the finished game was first released). It was free for a bit, at which point this post was originally written for the Freeware Garden, but not any more.