House Rules
Ability Scores
New characters are rolled with 4d6 for each ability score, dropping the lowest roll. At each level, one ability score may be increased by 1.
Feat Changes
Dodge: AC bonus applies to all attacks.
Toughness: +3 HP or +1 HP/level, whichever is greatest.
Death and Unconciousness
A character goes unconscious at -1 HP. A character dies at -(constitution score + character level) HP. Normal rules for bleeding to death apply.
Raise Dead and Resurrect spells exist, but persuading someone to cast them is generally difficult. Casting either spell requires someone to sacrifice a year of their life. (They are magically aged a year as the spell is cast.)
I'm also probably going to raise the spell level of Raise Dead, Resurrect, etc. by a couple levels. I may add additional rules around this as well.
Coming Back From the Dead
These aren't completely nailed down yet, but here's the gist:
Raising, resurrecting, etc. generally have an exorbitant cost (20,000+ gp) as well as a penalty to both the caster and the recipient. These penalties vary from religion to religion, and often involve such things as the caster aging a year or more. In addition, raising "unworthy" recipients may bring the wrath of one's god, so most clerics will be willing to raise just anyone with enough money. Getting someone raised is generally a challenge.
Raise Dead is no longer a 5th level spell. Any spell to bring back someone from the dead will be at least a 7th level spell.
Trading Skills and Feats
At the DM's discretion, a PC may switch an old feat or skill for a new one. Generally this involves the character finding a mentor, taking time to train, and possibly paying a fee.
Hit Point Rolls
All characters receive max hit points for 1st level. Thereafter, roll normally. A roll of 1 on a d6 and d8 may be re-rolled. A roll of 1 or 2 on a d10 or d12 may be re-rolled.
Wizards and sorcerers get d6 for hit points in stead of d4.
Cramped Quarters
In a corridor 5' wide or narrower, a -2 attack penalty is applied to large slashing or bludgeoning weapons. An additional -2 attack penalty applies if there is less than 2' of headroom.
In corridors 3' wide or narrower, a -4 attack penalty is applied to large slashing or bludgeoning weapons, and a -2 attack penalty is applied to medium slashing or bludgeoning weapons. An additional -4 or -2 attack penalty applies if a character must hunch over to fit in the tunnel.
Skill Checks & Ability Checks
If a natural 20 is rolled, it is not automatic success. Instead, roll another d20 and add the two rolls together. (If another natural 20 is rolled, add another d20 roll, etc.)
If a natural 1 is rolled, it is not automatic failure. Instead, roll another d20. Use -1 times the result as the value of the roll. (So, if you rolled a 1, then rolled a 7 on the second roll, your skill check roll would be -7.
Spontaneous Spells
A character does not need to prepare spells of level x ahead of time if he is capabl of casting spells of level x+4. For example, a 9th-level cleric (who can cast 5th level spells) does not need to prepare 1st level spells; he can cast them spontaneously.
In addition, 0th-level spells never have to be prepared.