Some Feats I've Devised

Battlewise

(Prerequisite: Wisdom 13 or higher)

• You may use your Wisdom modifier in place of your Dexterity modifier when determining Armor Class and Initiative.
• You have advantage on attempts to avoid being grappled, knocked prone, disarmed, shoved, or overrun.

Cunning Combatant

(Prerequisite: Intelligence 13 higher)

• You may use your Intelligence modifier to determine Initiative, Armor Class, and attack and damage rolls for weapons you are proficient in lacking the Heavy or Two-Handed properties.

Daggermaster

• Whenever you make an attack with two-weapon fighting using a dagger, you may make an additional dagger attack as part of the same bonus action.
• When you successfully hit with a dagger and had advantage on the attack roll, any hit is a critical hit.
• Whenever you critically hit with a dagger, treat its damage die as 1d8.

Diehard
(Prerequisite: Constitution 13 or higher)

• Death saving throws made by you are Constitution saving throws.
• Taking damage is not an automatic death saving throw failure, but you still die if you reach your hit point maximum expressed as a negative.
• On your third death saving throw success, you regain 1 hit point at the start of your next turn.

Divine Initiate

• Choose a channel divinity from the Cleric or Paladin class. You may use it once per short or long rest. Whenever it mentions your class level, you may instead use your character level.
• If you did not already have the ability to do so, you may use a holy symbol as a spellcasting focus.
• You use Wisdom for Cleric channel divinities and Charisma for Paladin channel divinities.
• Lastly, you gain the Divine Health feature.

Duelist

• If no creature other than the target of your attack is within 5 feet of you, you have advantage on the attack roll.
• If you hit a creature against whom you had advantage on the attack roll, you may add 1d6 to the damage roll of the attack.

Hearty Constitution

(Prerequisite: Constitution 13 or higher)

• You regain all your hit dice at the end of a long rest.
• Add your proficiency bonus to any healing or temporary hit points you receive, including each hit die you spend.

Master At Arms

• While wielding a Versatile or Two-Handed in both hands, or a weapon in each hand, you gain a +2 bonus to AC. This is cumulative with the Dual Wielder feat.
• While wielding a weapon in one hand  and no weapon or shield in the other, you gain a +2 bonus to weapon attack rolls.

Prodigy
(Prerequisite: Must already have a subclass)

• Add 1 to any one ability score of your choice. As normal, this may not increase any score above 20.
• Gain the first benefit of one subclass for your class other than the subclass you've already chosen.
• Whenever you would gain a feature in one of your subclasses, you may choose that level's feature(s) from any one of your class's subclasses.

[Weapon] Master

• +1 to either your Strength or Dexterity score.
• Choose a single weapon you are proficient in, or your unarmed strike. You gain +2 to attack and damage rolls with your chosen weapon, and may ignore damage resistance to your weapon, and treat immunity to your weapon as resistance.
• Additionally, you may choose to treat this weapon as if it had one of the following properties if it didn't have it before: Finesse, Light, or Reach. You may also choose to ignore the weapon's Heavy property in place of one of these properties.