The best example of this I can think of is the custard pie in King's Quest 5. You can use it in all kinds of ways, but you're screwed if you do as you need it for a bit right near the end of the game.

That's a nice way to do it; have a trap give you a special ending.

In Undertale, there's one situation where a death trap gives you an alternate game over screen.

Undertale Spoiler (rot13 encoded because it is a major genocide route spoiler; you can decode this at rot13.com):
Jura lbh svtug Fnaf ng gur raq bs gur trabpvqr ebhgr, ng bar cbvag va gur onggyr, ur jvyy fcner lbh. Vs lbh pubbfr gb fcner uvz ng guvf cbvag, ur uvgf lbh jvgu na nggnpx gung vf thnenagrrq gb xvyy lbh (naq vs lbh purng gb fheivir vg, gur tnzr fbsgybpxf). Bapr lbh qvr, lbh ner gerngrq gb n tnzr bire fperra jvgu n snfg irefvba bs gur qbtfbat cynlvat (vafgrnq bs gur hfhny tnzr bire gurzr) naq n zrffntr gung'f fbzrguvat yvxr "trg qhaxrq ba".

Me and my longtime best friend love those old Japanese gems like WotS from the PS1 & 2 eras.

Much thanks for the spoiler encoding as i've yet to beat Undertale lol. I'll get to it eventually in my massive game backlog lol.

That mention of the softlock kinda reminds me of the final conversation choice with the Dragonlord in Dragon Quest/Warrior 1, though that's not really a trap as it's pretty obvious that choice is the bad ending. Scared the crap out of me when choosing it the first time as the graphics just turn red lol.

That's reminded me of a point at the beginning of the GBA RPG Golden Sun. You're basically asked if you'll accept the responsibility of saving the world and if you say no you get a nice little epilogue text about the world falling into ruin before a game over screen.

It makes a refreshing change from Ocarina of Time's "Will you help?" "No." "Oh please!" "No." "Oh please!" "No." "Oh please!" "No." "Oh please!" "No." "Oh please!" "No." "Oh please!" "No." "Oh please!" "Yes!" "Oh I knew you'd help!".

Oh jeez, i've played Golden Sun, but I never knew about this LOL.

Nope, I ain't falling for that heterophobic trap.

edit: spelling.

I'm extremely contrary when it comes to games so I usually go out of my way to try the opposite of what the game wants. On this occasion it worked!

Dirty Harry on the NES has an actual trap room, the infamous "ha ha ha" room, where you enter a regular looking door, only to find yourself sealed in a room with no exit. That's it, restart the game.

Also, I was hoping this was about otoko no ko, commonly known as "trap".

Not another one. Take your paranoid delusions elsewhere please.

Dirty Harry NES was so hard and confusing I don't think I ever got that far lol. Interesting that a licensed game of that age had a non-linear level design though.

If you don't want to be spoiled, play the genocide route before decoding it; the spoiler is specific to that particular route through the game.

In the remakes of Dragon Quest/Warrior 1, I believe the result of chooing that choice was changed, but I don't remember what they changed it to.

Of course, that game is also known for its use of the endless question cycle:
* Dost thou love me? (Player chooses "NO")
* But thou must!
* Dost thou love me?
Repeat until player chooses "YES".

Later in the series, there's some finite length question cycles intended to steer you away from the bad choice. These can be distinguished by the fact that the message is different each time you choose the wrong answer. (Also, if the default choice is "No", then there's a good chance that "Yes" is the wrong answer here and choosing it enough times will lead to a bad result.)

I never knew there was a Dirty Harry game.

Die Hard sure, but not a Dirty Harry.

Which reminds me, anyone know of any good emulators that are Win 10 friendly in case I can't snag a NES MINI tomorrow?

Interesting about the remakes. I'll have to try those someday.

Ah yes, I remember that convo. Didn't saying yes grant health regen when walking? Or am I thinking of something else?

Terra Nova had a pretty harsh trap at a certain point. I won't say more, just... beware of traitors. It might seem you are up for an easy mission, but if you made yor researches and paid attention to details you could actually avoid to die a gruesome death.

It's not really what the OP asked, but still a great twist.