When the game lets you make an extremely dumb decision that kills you/gets you a game over/makes it impossible to win

[u/Zeekay89]

Basically what it says. The extremely dumb decision that can only end in your death, game over, or make winning impossible is a valid option you can choose.

Mass Effect 2. Morinth is an Ardat-Yakshi, an Asari with a genetic condition that causes the Asari mind meld to burn out her partner’s nervous system and give her a euphoric feeling. If you choose her over her mother, Samara, she says that Shepard is special and can survive where everyone else has died. She’s lying and you die like everyone else if you sleep with her.

Nier: Automata. There are a lot of unique game overs in the game that usually involve dying during certain events. A few involve making truly idiotic decisions. Engaging your self destruct inside the pressurized space station blows it up. You can remove a component that is essentially your brain and instantly die. You can eat a fish that is said to be extremely delicious but destroys the insides of androids.

Lords of Aswick. One possible scenario in this choose your own adventure game is that you take in one of the king’s bastards as your squire. The king just had a legitimate heir and started killing his bastards to secure his heir’s claim. Later on, you have the option to declare in open court that your squire is the king’s bastard. The next scene is your execution with bastard having just been executed before you.

[u/Neat_Information_737]

In Fallen London (amazing browser game) there's many such cases. Notable ones include jumping into a furnace the game explicitly tells you will kill you and achieve nothing, and the entirety of the Seeking Mr. Eaten's name storyline. It's the storyline that permanently bricks your account, and ruins your stats and accomplishments. 

[u/Gummy_Dragon → u/Neat_Information_737]

Jumping into the furnace is survivable if you acquire a secret quality that also requires enduring triple menace jail. SMEN is not.

Death in Fallen London means being in timeout for like two hours before coming back to life. If you spent several years grinding for Hespiridean Cider, you can revive instantly. What SMEN does to you is stick you in a storylet that can't be exited without playing any of the options... Except neither option actually lets you out. That account is completely unusable, forever.

SMEN requires significant story progression (at least Person of Some Importance and Cave of the Nadir) and can take several months to complete on its own, in a game that itself has years worth of content. And you are choosing to throw all of that away despite constant warnings that describe exactly what will happen to you and a permanent escape button that gets shoved into your inventory.