The bolded moves/items/abilities "slowly" heal you.
-Dream Eater (when target is asleep)
Dry Skin modifies HP depending on climate. During sunshine, the Pokémon with this Ability will lose 1/8 of their maximum HP at the end of each turn. During rain the Pokémon with Dry Skin will regain 1/8 of their maximum HP at the end of each turn.
In addition, Fire-type attacks do 25% more damage to these Pokémon, while Water-type attacks will have no effect, and heal ¼ of their maximum HP instead.
Ice Body causes a Pokémon to recover 1/16 of its maximum HP at the end of every turn when it is hailing. If a non-Ice-type Pokémon has this Ability, it will take no damage and still recover 1/16 of its total HP each turn during hail.
If the Pokémon is poisoned or badly poisoned, it will gain 1/8 of its maximum HP at the end of each of its turns instead of taking damage.
Rain Dish recovers 1/16 of the user's maximum HP at the end of each turn when it is raining.
Regenerator causes the user to restore HP by ⅓ of its maximum HP when switching out.
The HP stolen by HP-draining moves is increased by 30%. It affects the moves Absorb, Mega Drain, Giga Drain, Leech Seed, Leech Life, Dream Eater, Drain Punch, Horn Leech—and despite not being HP-stealing moves—Ingrain and Aqua Ring.
Restores 1/16 of the Pokémon's maximum HP (rounded down) each turn when held by Poison-type Pokémon; damages all other types by 1/8 of maximum HP each turn. Does not damage a Pokémon with Magic Guard.
Restores 1/16 of the Pokémon's maximum HP (rounded down) each turn when held.
Whenever the Pokémon holding it deals damage, it restores 1/8 of the damage dealt as HP.
Restores 10 HP when its HP drops to below ⅓.
Restores 25% HP when its HP drops to below ⅓.
When a Pokémon holds an Enigma Berry and is hit by a super effective move, it will recover ¼ of its HP. This effect is present only from Generation IV onwards.
Restores 12.5% HP, confuses Pokémon that dislike spicy food.
Restores 12.5% HP, confuses Pokémon that dislike dry food.
Restores 12.5% HP, confuses Pokémon that dislike sweet food.
Restores 12.5% HP, confuses Pokémon that dislike bitter food.
Restores 12.5% HP, confuses Pokémon that dislike sour food.
NOTE 1: This is it for now. I think i got it all.
NOTE 2: Will update with items in B/W2 if necessary.