Falling Rules
The way falling works in 3.5 edition Dungeons and Dragons, a character takes 1d6 damage for every ten feet he falls. The first time you look at this, there does not seem to be anything wrong with these rules. 1d6 is a lot of damage for a low level character, but practically nothing for a higher level character. This allows for spectacular scenes at higher levels, with players who are more prone towards self-sacrifice and glory willfully throwing themselves from great heights to achieve a greater purpose. However, if you think about it, this system is not realistic.
Let us take a fall from 40 feet. Since the average roll on a six sided die will come to 3.5, the average amount of damage taken from that fall will be 14. Given ten hit points of unconsciousness, this means that a first level spellcaster with any constitution bonus or other way of boosting his hit points could expect to be able to survive a fall from 40 ft, a fall that would kill most people. The same goes for most NPCs, as many have a d6 hit die. Most could be thrown from 40 ft and they could expect to survive it over half of the time. Then all they need is someone nearby to make a simple DC 15 heal check, and the victim will be fine, bruised and unhappy, but not dead.
Keep in mind, that is assuming average values for the damage. The maximum amount of damage that could be dealt from a fall of that height is 24. Once again, allowing for ten hit points of unconsciousness, that means that someone would need 15 or more hit points to survive the fall. This is not all that difficult to get, a barbarian would only need a 16 or higher constitution to survive the fall, and a dwarven fighter could feasibly get a 20 constitution and have enough HP to live through the fall. What this means is that either of these characters, and any other with 15 or more hit points, could jump off of a 40 ft high roof or similar structure, with absolute confidence that they would survive at least the fall. In fact, given the average of 14 points of damage from a fall of this height, a character with 15 HP could, approximately half of the time, fall from a height of 40 ft and be running again on his next turn.
To make this more realistic, we suggest an exponential increase in damage. A 10 ft fall still deals 1d6 damage, and a 20 ft fall still deals 2d6. However, a 30 ft fall deals 4d6, and a 40 ft fall deals 8d6, each time the damage doubles. Under this system, a 40 ft fall would deal an average of 28 damage, which would almost certainly kill a 1st level character, with only a handful of exceptions. That way, it is much more realistic when a character is thrown off of a roof.