"Single-Life" Hardcore Mode
This is a form of Hardcore Mode in which, not only are conditions at their most difficult, but the player also has but one life to live before the game resets.
Released in 2000, the action RPG Diablo II featured persistent online multiplayer and handled closed Battle.net multiplayer game saves server-side. Hardcore mode, while presenting no changes in difficulty, made death of a player's character permanent and irreversible, including the loss of all progress and equipment. Many hack-and-slash RPGs after Diablo II also followed this concept, and in games like Minecraft and Terraria, death also means the end of the world that players have worked so hard to create.
A variant on this is to limit the number of saves a player can make before disallowing saving altogether. Dead Space 2 was infamous for this, as its Hardcore mode would only allow players to save three times before blocking them from the save stations, forcing them to restart from their last save point if death occurred.
Hardcore Mode in Shooters
Hardcore mode in shooteres was largely popularized by the Call of Duty series, which was one of the first series of games to incorporate the mode into its online play. This modifier applied only to multiplayer matches, making them more realistic by removing HUD elements and increasing the damage dealt by each bullet. Other multiplayer shooters were quick to pick up on this, including Call of Duty's biggest rival, Battlefield.
Before long, the concept of a hardcore mode began to stretch beyond the boundaries of a multiplayer game. Single player games began including it as well. One of the earliest examples of this is Fallout New Vegas, which played similarly to Fallout 3 under normal conditions but which became far more challenging on Hardcore mode. Food and radiation were handled much more strictly in Hardcore mode, and if players didn't eat and treat their injuries regularly, they would die just as they would in real life.
Over the last few years, the monicker of Hardcore has grown to imply many different meanings. Overall, though, players who play under this setting can look forward to a brutally challenging experience. Below is a summary of each variation on the term.
Multiplayer: In games such as Modern Warfare 2 and Battlefield Bad Company 2, Hardcore mode is a completely separate list of modes that is segregated from the normal matchmaking community. Players who play Hardcore online are treated to a reduced or completely eliminated HUD, no targeting reticule on their guns, and lower health.
Single Player: Games such as The Gunstringer or Fallout New Vegas feature Hardcore modes which require players to take more variants into consideration before acting. For example, in Fallout it is possible to starve to death in Hardcore mode. Starvation is not possible in the normal mode.