Page number and name of optional or variant rule:
If you have any I missed, please let me know and I'll add it.
EDIT: Added 2 variants on p140 regarding potions and scrolls
22 Renown
50 Feywild Magic
52 Shadowfell Despair
59 Psychic Dissonance
59 Blessed Beneficence
59 Pervasive Goodwill
60 Overwhelming Joy
60 Hunter's Paradise
60 Beast Transformation
61 Intense Yearning
61 Immortal Wrath
61 Power of the Mind
62 Mad Winds
62 Abyssal Corruption
63 Prison Plane
63 Vile Transformation
63 Cruel Hindrance
64 Pervasive Evil
66 Bloodlust
66 Law of Averages
66 Imposing Order
67 Planar Vitality
93 Loyalty
96 Cleric: Death Domain
97 Paladin: Oathbreaker
131 Training to Gain Levels
140 Potion Miscibility
140 Scroll Mishap
141 Wands That Don't Recharge
230 Alternatives to Epic Boons
241 Only Players Award Inspiration
251 Flanking
252 Diagonals
253 Facing
263 Proficiency Dice
263 Ability Check Proficiency
264 Background Proficiency
264 Personality Trait Proficiency
264 Hero Points
264 New Ability Scores: Honor and Sanity
266 Fear and Horror
266 Healing: Healer's Kit Dependency
266 Healing: Healing Surges
267 Healing: Slow Natural Healing
267 Rest: Epic Heroism
267 Rest: Gritty Realism
267 Firearms
267 Explosives
268 Alien Technology
269 Plot Points
270 Initiative: Initiative Score
270 Initiative: Side Initiative
270 Initiative: Speed Factor
271 Action Options
272 Hitting Cover
272 Cleaving Through Creatures
272 Injuries
273 Massive Damage
273 Morale
285 Creating a Race or Subrace
287 Modifying a Class
288 Spell Points
289 Creating a Background