Portal:Fallout: New Vegas
In this mode, the Courier must stay hydrated, eat periodically and have a regular sleep cycle. stimpaks and RadAway work over time rather than instantly, and to restore critically damaged limbs, you must use a doctor's bag, hydra or visit a doctor. Finally, ammunition has weight, so you can only carry a limited amount. In addition, recruited companions can die permanently, whereas they are only rendered unconscious in casual mode.
The game takes place in 2281, four years after the events of Fallout 3, and thirty-nine years after Fallout 2. The Courier, the player's character, is meant to deliver a package from Primm to New Vegas. However, the Courier is intercepted by the Great Khans and Benny, who leave the Courier for dead in a shallow grave.