Instant Death

Time and again I've come across this game design decision that only makes sense in a few places and that concept is instant death.  Instant death comes in a lot of varieties: you touch the spikes in a Mega Man game (harsh but fits within the harshness of the game), you fall outside the world (necessary for play to continue even if it's a bit ridiculous), an enemy uses a spell on you that has a small chance of instantly wiping you out.  It's that last one that gives me the biggest problems, especially when there is no way to dodge said spell.

I can't come up with one legitimate reason why it would be okay that a random, unavoidable die roll could instantly bring your game to a halt.  It doesn't show skill on the computer's part.  Since the player can't do anything to stop it, it's not a test of skill for the player.  It's like creating a game where the end result is a die roll to determine who wins.  No one would want to play that game because player input isn't even needed.

The only two cases I can come up with where any instant death is viable is if you're building an arcade game or punishingly difficult game where the purpose of the game is to frustrate the player/make them die frequently or if a player falls down a pit or outside the world where there isn't a way to get back normally.  This last one is actually completely necessary because the alternative is to make the player wander around trying to figure out how to escape what is usually a bug in the level design and then either restart the game or (more likely) turn it off and never play again.  Sure it's frustrating to die because of this, but at least it's (usually) the player's fault for jumping in a pit.

Games that do have the instant kill spells/attacks generally give ways to minimize or eliminate the chances of the problem by giving equipment they can wear to make those never successful, but that's not fixing the problem.  That's working around the problem and taking up a valuable equipment slot the player could use to equip something that makes them feel awesome instead of wasting it on something to stop bad game design from killing them.  At that point, you might as well just eliminate that equipment slot and the instant kill attack at the same time and be done with it.  You've eliminated the interesting choice from the game for all players except for people who like to gamble with their chances of success.  If that is the purpose of adding instant death, then there are better ways to achieve it.  You could give the player the risky attack so it's their choice to use it or not.  You could add a casino to your game so players can get that feeling outside of the combat.

There are board games where the winner is decided by random luck like this (e.g. Candyland and Chutes and Ladders).  There's a reason people stop playing these games once they grow up a little.  Winning or losing a game through pure luck is not an enjoyable experience for anyone.  So eliminate the random chance and eliminate instant elimination.