Here are some of the House Rules that are going to be used in the next campaign I run later this year after the current one wraps up. A lot of these House Rules have been used in the past and are currently in use now:
* Ability scores are rolled using 4d6 and rerolling only 1s. Assign rolls accordingly before assigning racial modifiers. Reroll stats if the total bonus from all stats is less than 0. :: Used since 1994 ::
* Untrained cross class skills do not exist. A character can purchase any skill that does require training at the normal ratio, regardless of class. Skills that require training, such as Decipher Script, may only be chosen at cross-class skill ranks unless they are listed as a class skill in the class's Class Skills section. :: Used since 2001 ::
* Action Points, Character Traits, and Weapon Proficiency Groups from Unearthed Arcana. :: New ::
* Defense Bonus from Unearthed Arcana. Armor provides damage reduction equal to the armor bonus it would normally give. Shields add to Defense Bonus :: New ::
* When rolling to stabilize, instead of rolling percentile dice, roll a Fortitude save with a DC of 15 + the amount below 0 your character is. For example, if your character is at -3 hit points, the Fortitude save to stabilize is 18. :: New ::
* Spells cast by a spellcasting class now have a modified DC for spells. The difficulty class for any spell is now equal to 10 + 1/2 appropriate spellcaster level (rounded down) + the caster's appropriate attribute modifier. This may cause the highest level spell you can cast to not have the highest save DC it possibly could, but it also means the DC for any given spellcaster is always the same and doesn't have to be recalculated for each spell level (a minor bit of math true, but every bit helps). :: New ::
* Before any character can enter into a prestige class, he or she must pass a test-based prerequisite set forth by the DM. :: Used since 2003 ::
* Weapon Specialization and Greater Weapon Specialization Feats: Classes other that fighters may select these feats, although there are a few limitations:
1. Classes with a good base attack bonus progression may take Weapon Specialization at 8th-level and Greater Weapon Specialization at 16th-level.
2. Classes with an average base attack bonus progression may take Weapon Specialization at 12th-level and Greater Weapon Specialization at 20th-level.
3. Classes with a poor base attack bonus progression may take Weapon Specialization at 16th-level and may never take Greater Weapon Specialization.
4. Priests may take Weapon Specialization and Greater Weapon Specialization for their deity's favored weapon as if they were a fighter. All other weapons follow their base attack bonus progression as stated above.
:: Used since current campaign ::
* Critical hits are handled differently. Any weapon with an increased threat range (due to weapon characteristics, feats, spells, or other abilities) now has an increased critical multiplier. If a weapon has a critical threat range of 19-20/x3, then increase the critical multiplier by 1, making the critical multiplier x4 and reducing the threat range to 20. Spells and magical abilities that increase the threat range now increase the multiplier. For example, a longsword normally has a threat range of 19-20/x2. Its new threat range under this system is now 20/x3. If the spell Keen Edge were then cast upon the longsword, it would now increase the multiplier of a longsword to 20/x4. :: New ::
* An extensive critical failure chart too extensive to post. :: Used since 1994 ::