I like what
@Kes said, as I think horror games need to be treated different from the rest in this discussion, but yes on-map game over's through events or interaction usually works in horror games and make some sense, but I still get annoyed if checkpoints are far away from one another. Otherwise, I think it could work well in those instances!
Still, it needs to be balanced well, not every single thing every few seconds should give a game over, I think.
On maps in any other RPG made in RPG Maker though, I don't know if map instant death would work. At first thoughts, they sound annoying to me and probably very dislikable, I can't say I know an example where it works, but I'll leave my opinion as that. To me, it just sounds an annoying idea for players.
I also don't like joke games that do this either, I actually can find a joke game funny in some instances, but instant KO's on map events a lot still just comes across as annoying to me, even in those games.
In battles though? An instant death possibly on a single party member may be interesting and add a challenge to the battle. I've done that before on a final boss in a game I developed, but had to balance it carefully.
I think it worked well. One person told me they enjoyed that a lot. I had 3 party members in that battle as well, so it was a bit threatening.
However, I had three other people give me feedback, before the positive comment. They said they didn't realize there were revive item's to pick, because I spelt the Revive Potion description as the same as the normal HP Restored Potion by mistake, whoops!
That definitely didn't go down well, but interestingly enough they didn't criticize the mechanic of an instant death on a character, only the problem that they couldn't revive, which of course is an example to say it'll have to be balance if you plan to use the instant KO on one single party member technique. (In my case, after fixing the description, player have added revive items before the fight, a few more extra than enough for me to beat the boss with. And one of those 3 party members could cast revive as a skill too, I like the idea myself, and I used it once, not often.)
But ALL of your party members, in a battle, getting a instant full game over from a skill being used? I definitely can't see this as being a good idea, nor working at all. Prove me wrong, maybe, but my first thoughts are I'd quit the game and how annoying that would be.