I'm fully shifting over (up?) from 3.5e/PF to 5e, so most of my houserules are now obsolete! Here, for your perusal, is my final houserule setup, complete and moved on from after ten years of tinkering.
==Characters and Character Creation==
*Ability scores: point buy 30, starting at 8, as on page 169 of the Dungeon Master’s Guide.
*All characters begin with 1,000 gold and an adventurer's kit containing a backpack, 5 torches, flint & steel, 50' hempen rope, a waterskin, and clothing of your choice (excluding courtier's outfit, noble's outfit, and royal outfit). (21 lb., not counting gold and clothing.)
**Characters beginning at higher than 1st level start with standard WBL for their ECL or 1,000 gold, whichever is higher.
*Characters begin at minimum XP for the ECL of the lowest-level member of the party they join.
**If your character dies and is not resurrected (or retires, or becomes an NPC, or is otherwise unplayable), you may begin a new character at 75% of the previous character's experience total.
**In either case, new characters are limited to 5 class levels by default, with the remainder of their ECL taken up by racial hit dice and level adjustment.
**However, new characters may, under some circumstances, begin with more than 5 class levels provided they have a backstory that explains their exceptional skill and power relative to the rest of the setting (very few NPCs ever exceed level 6-8), and why history hasn't heard of them before now, in a satisfying way.
*Hit dice are maximized at first level. At each level after first, you gain half your hit die, plus 1 (plus your Constitution modifier), as follows: d12 = 7; d10 = 6; d8 = 5; d6 = 4; d4 = 3
*A character may have up to 2 flaws and up to 1 trait. In addition to the base flaws in Unearthed Arcana, consider the flaws published in Dragon Magazine issues #324-329 and #333.
*Characters take no experience penalties for multiclassing. Instead, they gain a minor bonus based on their racial favored class.
*For the purpose of the epic-level prerequisite for [epic] feats, prestige classes, and other options, a character is considered epic at 10th level instead of 20th level. After 10th level, regular feat slots may be used to acquire [epic] feats. All other prerequisites still apply.
**All [epic] options (feats, prestige classes, and so on) with skill prerequisites have those skill prerequisites reduced by 10, to a minimum of 13 and a maximum of 21. Similarly, [epic] options with base attack bonus prerequisites have those prerequisites reduced by 10, to a minimum of 10 and a maximum of 18.
**There are no epic spells. If you take the Epic Spellcasting feat, you may use your epic spell slots only to prepare or use non-epic spells, with or without metamagic applied.
*You may ignore regional requirements for feats, prestige classes, and other options, except that you may not select two options that have conflicting regional requirements.
*Fractional BAB and fractional saves may be used if you so desire.
*Animal companions, special mounts, familiars, and psicrystals all gain feats and ability score increases by their (effective or actual) HD.
*Caster level equal to half class level (e.g. ranger, paladin, etc.) is no longer a thing. Such classes have a caster level equal to their class level.
*Any class, race, or template that grants a Smite special attack (e.g. Paladin, Soulborn, Fiendish Creature, etc.) with uses per day instead grants the same number of uses per encounter.
*A few classes have been tweaked.
*Any prestige class that advances spellcasting from another class ("+1 level of existing spellcasting class" and the like) advances the full suite of: spells per day, spells known, and caster level; even if the text for the prestige class omits one or more of those aspects.
*If you have the ability to learn a spell from any spell list (e.g. by taking the Extra Spell feat), and the spell you wish to select appears on multiple lists, use the spell level of the first list it appears on of the following: sorcerer/wizard, cleric base list, druid, bard, paladin, ranger, any other base class, any cleric domain, any prestige class.
*Characters gain retroactive skill points when their Intelligence modifier increases.
===Level Adjustment===
*All listed level adjustments are divided by 2 (rounded down, but with a minimum of 1 for LAs that aren't already zero). Sum your character's total LA before dividing.
*Monster class progressions (e.g., from Savage Species) may be used. Most will need to be adjusted to fit the race's new level adjustment (see previous rule). A character is not required to finish their monster class progression before entering another class; however, a character may not have more class levels than monster levels unless their monster class progression is complete. Once you have completed your progression in a monster class, the “empty levels” that do not add hit dice may be reduced like level adjustment, as below.
*A character may have one bloodline (from Unearthed Arcana). A bloodline level counts as a level adjustment and nothing more; it does not count as a class level for any purpose. However, once you have taken all the bloodline levels you are required to take (1 for Minor, 2 for Intermediate, 3 for Major), they may be reduced like level adjustment, as below.
*Level adjustments may be reduced or "paid off" as per the Unearthed Arcana/SRD rules.
==Situational==
*If a PC or a major (e.g., named) NPC confirms a critical hit, they draw from Paizo's critical hit deck. All others simply multiply the damage as usual.
*If any character rolls a total of 0 or lower on an attack roll, it is an automatic critical fumble, and they draw from Paizo's critical fumble deck.
*The experience of dying and returning to life leaves a person drained of vitality even beyond the loss of a level. Upon resurrection, a character is aged a number of years equal to 1d20 minus their Constitution modifier (minimum 0. A negative Constitution modifier can increase the number of years aged). The true resurrection and true reincarnate spells negate this effect. These years are added to the base adult age in the case of the reincarnate spell.
*A character is considered dead if he reaches negative his Constitution score or negative 10 hit points, whichever is further from zero.
*Characters have a mental age and a physical age. If they are subjected to an artificial aging, youthening, or aging-prevention effect, it normally affects only their physical age. Physical age penalties apply (or are removed) when the character's physical age advances (or reverses) an age category; mental age bonuses apply (or are removed) when the character's mental age advances (or reverses) an age category. Death from old age only occurs when physical age reaches a maximum; one cannot die of old mental age.
*The Giant's diplomacy fix is in effect.
*You may split actual movement around a non-moving move action. Example: move 15' to a door, open it, and then go through the doorway that same round using the rest of your movement.
*All Trained Only skills can be used untrained at a -10 penalty.
*Spellcraft may be used in place of Psicraft, and vice versa, at a -10 penalty. Use Magic Device may be used in place of Use Psionic Device, and vice versa, at a -10 penalty.
*If a temporary source with a duration grants a Constitution bonus (e.g. Barbarian Rage, Bear's Endurance, etc., but not Amulet of Health), the extra hit points granted are temporary hit points which expire when the Constitution bonus goes away. They are lost first, and no real hit points are lost when the duration expires.
*When a spell almost can but can't quite achieve a desired effect, or achieves the desired effect with the most generous reading but not a narrower reading (for example, using heal to cure natural insanity, or using protection from evil to ward off a [compulsion] that only grants control over the target in the broadest sense), a caster of spells or SLAs can alter a spell's effect slightly on the fly. This requires a caster level check or spellcraft check at a difficulty of 15 plus twice the level of the spell to modify.
**Manifesters of powers and PLAs can do the same with a manifester level check or psicraft check against DC of 15 plus twice the power level. Initiators of maneuvers can do the same with an initiator level check or a martial lore check against a DC of 15 plus the maneuver level. Users of natural, extraordinary, and supernatural abilities that aren't included in the above can do the same with a HD check against DC20.
*The soft cover and shooting-into-melee rules are amended/clarified in the following way:
**Using a ranged weapon, if you shoot into somebody in melee combat with somebody else, or there's somebody between you and your target, you get -4 to your attack. These penalties do not stack. Precise Shot negates both penalties.
**Using a reach weapon, you get a -4 to your attack if there's somebody between you and your target, but not if your target is merely in melee with other folks who aren't in the way. The new Polearm Precision feat negates this penalty.
**You can use a reach weapon to attack a Large or larger creature even if it is adjacent to you, by targeting a non-adjacent square occupied by the creature. However, this attack takes the -4 penalty for attacking through a creature.
*You may level up immediately when you gain enough experience to do so, no matter where you are. You immediately gain your full new hit points (i.e., your current hit points go up, but your damage remains the same), but you don't immediately gain anything that you would need a rest for (such as new spell slots, new spells prepared, additional power points, etc). You may elect to delay leveling up as long as you wish, but for the purpose of XP awards you are treated as being whatever level you've earned (so if, e.g., an artificer delays leveling up from 2 to 3 to use up their craft reserve, they're still treated as an ECL3 character for the purpose of future XP awards), you must still apply your levels in the correct order, and you must apply each level in its entirety at the same time.
==Complete List of Permitted Sources==
===Explicitly Permitted Sources===
*The d20 System Reference Document
*The High Seas Reference Document
*Arms and Equipment Guide
*Book of Exalted Deeds
*Book of Vile Darkness
*Cityscape
*Complete Adventurer
*Complete Arcane
*Complete Champion
*Complete Divine
*Complete Mage
*Complete Psionic
*Complete Scoundrel
*Complete Warrior
*Deities & Demigods
*Draconomicon
*Dragon Compendium (except Dvati)
*Dragon Magic
*Drow of the Underdark
*Dungeon Master's Guide I
*Dungeon Master's Guide II
*Dungeonscape
*Eberron Campaign Setting
*Epic Level Handbook
*Expanded Psionics Handbook
*Fiend Folio
*Fiendish Codex I: Hordes of the Abyss
*Fiendish Codex II: Tyrants of the Nine Hells
*Frostburn
*The Giant's Articles (excluding the Polymorph rules)
*Heroes of Battle
*Heroes of Horror
*Libris Mortis
*Lords of Madness
*Magic Item Compendium
*Magic of Incarnum
*Manual of the Planes
*Miniatures Handbook
*Monster Manual I
*Monster Manual II
*Monster Manual III
*Monster Manual IV
*Monster Manual V
*Oriental Adventures
*Planar Handbook
*Player's Handbook I
*Player's Handbook II
*Races of Destiny
*Races of Eberron
*Races of Faerun
*Races of Stone
*Races of the Dragon
*Races of the Wild
*Sandstorm
*Savage Species
*Spell Compendium
*Stormwrack
*Tome of Battle - Book of Nine Swords
*Tome of Horrors, Revised Edition
*Tome of Magic
===Sources Sometimes Permitted With DM Review===
*Dragon Magazine
*Ghostwalk
*Unearthed Arcana (some elements used, some elements not used)
*Weapons of Legacy
*3.5e content on http://www.wizards.com
*most other 3.5e Wizards of the Coast-published sources
*most 3.0e Wizards of the Coast-published sources (content that hasn't been updated to 3.5 only)
*some third-party sources
*some Pathfinder material
*some reputable GitP-vetted homebrew
===Explicitly Banned Sources===
*http://www.dandwiki.com (use the hypertext d20 SRD instead to be sure of avoiding homebrew)
*most other homebrew
