What is NetHack?
NetHack is a roguelike from the late eighties where the player is attempting to obtain the Amulet of Yendor and ascend to become a demigod.
Being a roguelike, it's defined by frequent and permanent deaths. At the same time it rewards careful play and a smart player can escape almost any situation.
Why is it awesome?
Unlike most modern games there are an absurd number of interactions you can do, that range from killing an enemy by turning it to stone with a dead Cockatrice to polymorphing into a dragon, laying eggs, and having them hatch as tamed baby dragons.
And then there's the ways to die. Most of these have happened to me...
-Getting seduced by a Nymph who then steals your Wand of Death (that you hadn't identified yet) and zaps you with it.
-Casting Force Bolt in a store and destroying potions you can't afford, causing the shopkeeper to attack you.
-Drinking an unidentified potion to figure out what it is. It's Paralysis - something finds you and kills you.
-Trying to pickup a Cockatrice while not wearing gloves.
-Taking off you armor to climb over a boulder and getting murdered by a crazed Elf.
-Trying to get the Lady of the Lake (who apparently lives in a fountain) to give you Excalibur. Except you're doing it Minetown and the guards don't take kindly to you messing with their water supply.
-Trying to eat a giant corpse while not hungry and choking to death.
Sounds like Dwarf Fortress...
That's because it has a lot of similarities, both in terms of well over 50 different commands and an ugly ASCII interface. Fortunately, there's a pretty good GUI available (http://www.darkarts.co.za/vultures
) that provides both graphics that let you tell what's going on and the context menus necessary to figure out what's happening. When in doubt right-click on something.
You've convinced me. Now what?
You can go one of two ways either play completely unspoiled or read http://nethackwiki.com/wiki/Main_Page
I did the latter and it still took me nearly a month and many, many tries to finally get a character entirely through the game. And even then, mostly because I got very lucky with being granted wishes from magic lamps.
What role should I play?
(Lawful Dwarf) Valkyrie and Barbarian are usually fairly easy to get started with.
Anything else I should know?
If you have a smartphone, it's pretty much guaranteed that there's a NetHack port for it. Playing without the keyboard can be a little painful though.