We've talked about exploding dice (vile), and critical hits (pathetic), but there is one other thing that I hate, and that's the tails of the coin, assuming that a critical hit is heads: fumbles.
I talked about the rule of 1 and 20 last time and what that means in terms of success and failure. Summed up: you will always have a 5% chance of success and a 5 % chance of failure, regardless of your character's scores, bonuses, penalties, and relative ability.
Whenever critical hits are brought up the question that is there with it, unnoticed by the party goers at first, but eventually making its presence known like a bad oyster at the roast, is the evil twin of the critical hit, the anti-critical hit, the Lex Luthor to the Superman that is the critical hit: the critical failure, or critical fumble, or just fumble.
I hate that too. I feel it is a necessary evil, however, for anyone that wants to employ the critical hit rule. It provides the counter-balance to all the good fortune of the crit. It is as though the universe must be balanced, and lo the fumble did arrive upon the scene. In your basic D20 system a fumble is a bit of bad luck, over and above the usual penalty of failure (which is to not succeed) whenever a natural 1 is rolled on the die.
Now consider what the penalties are for failure already.
1. You do not succeed at whatever you are attempting. That's a pretty hefty penalty in and of itself. If you are attempting to catch a priceless Faberge egg before it hits the ground and you fail to do so, your prize is destroyed. That's a pretty hefty penalty. In combat this means you have not defeated your enemy, thus you extend the combat and your chances of being defeated yourself have increased.
2. If you fail at a to hit roll in combat, that is another chance for your enemy to roll to attack you. Ideally you want combat to be over in as short a time as possible, provided that you are the one still standing when it is over.
For example, you have 12 hit points and you need to roll a 15 to hit your opponent. He has 12 hit points and he needs to roll a 13 to hit you. Both of you will do 1-6 points of damage per hit. Logically you can withstand between 12 and 2 successful blows depending on the damage roll. If you miss on your first attack and your opponent hits, your total time left in combat is statistically shorter than his. Failure already carries a pretty hefty penalty.
The fumble then is a way to add insult, often painful insult, to injury.
Unless there is a table for it, the basic rule in games that have fumbles is sort of a DM's creative choice. The guidelines in the AD&D 2e Dungeon Masters Guide suggest that whatever happens, the player should basically lose his next attack as he recovers from the fumble, perhaps picking himself up off the floor, or recovering his lost weapon. In extreme cases of DM Dickbaggery this could result in a whole new attack roll where the player hits himself, his friends, or that priceless magical artifact they came to steal in the first place, causing handfuls of dice of destruction and ruining the whole quest.
Don't laugh, I've had DM's with a douchbag quotient far higher than is required for that. That would be a simple fumble to those assholes.
The critical fumble can be a source of great humor, and I like a bit of humor, but it is just as likely that it will ruin your night at the table. The critical fumble is guaranteed to ruin your night in one of two ways, if not both at the same time, and that sometimes happens as well.
1. When it happens just when you most don't need it to happen. Remember the rule of 1 and 20? 1 always fails and failure is already a penalty. So when you are in that life or death situation from which heroes are born and death is the most likely outcome, to roll a 1 is a bit disheartening, even if you needed a 19 just to hit. You were probably going to miss, you did, after all, have a 90% chance of missing. Should you heap a fumble onto that? You were hoping for that heroic 19 or 20. You might have rolled and 18 and said, "So close!" but instead you rolled a 1. In your mind it could not have gotten any worse, even though it is honestly no worse than any of the other numbers 2-18. It's still a miss. You NEEDED that 20, you rolled a 1. Or maybe you just needed it to not be a 1, and you rolled a 1. Now you are looking at a counter attack that will probably end this character's career, all because you heroically entered battle with only 1 hit point left. You dumbass.
2. Remember when I said you should not consider your dice rolls a measure of your personal human worth? On the flip side of the above example is the can't miss roll, where you'd actually need to roll a -2 to miss. Of course 1 always fails, so despite the fact that you couldn't miss, you always had that 5% chance of missing. Hey, combat is chaotic, things happen.
Were this to also be a fumble, that's just insulting and cruel. Your skill is such that you are so far beyond your target that you have only a 5% chance of missing, and yet now you are saddled with some sort of improbable outcome where you chop your own foot off? Or better yet, you swing wide and kill the cleric. That will make you put your dice into your Crown Royal Bag in shame and leave the table.
Because you make these characters, and you play them (hopefully with some intelligent tactics and decisions) and you start to care for them. You start to see the ranger you rolled up at first level, now at 8th level, as an important and skilled figure in the world, a mover, a shaker, a hero. The numbers are in your favor. It's bad enough to roll a 1 and know that it will always miss, but to roll a 1 and have your DM put you into some "hilarious" comedy routine of painful and embarrassing slapstick, that's just too much. Now your family heirloom sword has flown out of your hand, backwards, and into a lava pit, all because you rolled a 1 and it wasn't enough to just miss, the DM felt that such a major boner deserved his best Three Stooges treatment.
Both of the above examples share something in common above and beyond the failure aspect: they are completely random. That's right, they are completely at the mercy of a single 20 sided die which happens to have 2 numbers that will come up 5% of the time (each, not together). Just as the critical hit is a "reward" for good luck, the critical fumble is a "punishment" for bad luck. Note the quotes. These values already carry a reward and punishment called success or failure. Fumbles, like critical hits, are just bullshit.
For the sake of completeness, I might as well tell you that games with exploding dice also have fumbles, but how they work varies wildly depending upon the system. The most common example of a fumble in an exploding dice system, at least as far as my experience and study can determine, is something Deadlands called "going bust". Being a Weird Western game, Deadlands was fond of using poker terminology (such as Acing for rolling the highest value on the die, or getting a Raise when you exceeded the target number by 5 points).
Going bust simply meant rolling more 1s than any other value. You roll 6 d6s and get 5, 3, 1, 1, 1, 1, you just busted. Now in that game the GM (called the Marshal) was expected to put some interesting twist or complication into the scenario to make your life hell. In other games with exploding dice the lowest possible value (typically a 1) automatically removes a successful roll. So let us say you need to roll a 4 or better and you roll those bones and get 5, 4, 2, 3, and 1. Your 1 would remove one of your successful dice, usually the highest, so you'd net 1 successful die (the 4). If you'd rolled two 1s, then you'd have lost both successes and failed. If you'd rolled three 1s, you would have gone bust again. Pretty nasty, eh?
Again, some games have their own rules for when those fumbles happen, often depending on what you were doing. A spell might backfire if you fumble. You might shoot your buddies if you fumble. You might get the exact opposite reaction from a crowd than the one you intended if you fumble. The point here is that it's worse than just failure, and as we've established, failure already carries a penalty. It's called failure.
Please remember that this is all just my opinion. Don't let the math fool you into thinking this is some logical or scientific fact. Of the three cases, exploding dice, critical hits, and critical fumbles, the one I can most live with is actually the fumble. I hate exploding dice because they destroy the game flow and lead to impossible and thus game disrupting outcomes that remove player incentive to use their brains. I hate critical hits because I see them as disruptive, but also a reward for luck masquerading as skill. I hate fumbles because they are often embarrassing and inconvenient, but that is why they are the least offensive to me of all them. With a good GM and a healthy sense of humor, the fumble can be entertaining, humorous, and lead to even more game fun as you try to undo what has been done. A simple breaking and entering to obtain the stolen crown for the king can lead to an entirely new set of adventures as you attempt to solve the even bigger problem you created when you dropped the crown and it was swallowed by a giant carp. From adversity comes adventure!
But then that same crown and carp scenario need not be the result of some ridiculous 5% screw up. A simple failure could lead to the exact same scenario and won't leave you feeling like an asshole. In the end, I can do without critical fumbles. A fumble is a failure, plain and simple. Sometimes you roll to attack and you miss because the other guy is better and sometimes you roll and fail because the sun got in your eyes, but you don't need a special roll to tell you that. That is all part of playing the game.