I've got a handful of feats that I've been using in some homebrew games.  I wanted to see the thoughts of D&DB; the good, the bad, the broken, the suggestions, etc.

LATENT PSYCHIC

• Mage Hand Cantrip, but Mage Hand is Invisible.
• Detect Thought, once per long rest.  CHA based
• Telepathy (30 feet).  You do not need to have a shared language, but the creature needs to understand a language and have an intelligence of 3+
• Every time you use one of your psychic abilities, you give off an aura.  The DC to notice your Aura is 8 + CHA Modifier + Proficiency.

RUNE OF THE WARBLADE

• You have a Rune on your body that enables you to summon a fragment of the impossible weapons.
• Bonus action to activate.  Lasts 1 minute. Not considered concentration. Usable once per long rest.
• The blade is considered a Simple Weapon that you are Proficient in.  It has the Finesse, Light, and Thrown (20 / 60) properties. If you drop, or throw the weapon, you may summon it back as a bonus action. If the blade ends it’s turn not in your hand, it dissipates.
• The blade deals 1d6 Force Damage.  At 3rd level, this increases to 2d6 Force Damage.  At 5th level, it becomes a +1 Weapon (2d6 +1). At 11th level, it increases to a +2 Weapon (2d6+2), and at 17th level, it increases to a +3 Weapon (2d6+3).

KI ADEPT

• +1 WIS
• You gain 2 special Ki Points.  You may use these to fuel the ability listed here, or any regular ki abilities you have.  These points recover after a long rest.
• Slow Fall.  1 Ki Point. As a reaction, you reduce your fall damage by 5* your proficiency modifier. (Monk abilities replace this)
• Step on the Wind.  1 Ki Point. You may disengage as a bonus action.

I will say I have not built these feats in D&DB for my own players to use.