Hair-Raising Potion -
Hate Potion -
hellebore -
Hiccuping Solution -
horned slugs -
horned toads -
human parts
ingredients: include rat tails
Exact effect unknown
(CS13)
ingredients: unknown
Reveals the worst faults and habits of the target person to the drinker
Recommended by the Daily Prophet's advice columnists to help witches and wizards get over emotional attachments to people who don't love them (DP).
c.f. Love Potion
According to 
botanical.com,
there are several kinds of hellebore. The name comes from the
Greek words 'elein' (to injure) and 'bora' (food), indicating that hellebore
is poisonous. In some belief systems, it's been believed to be a purgative,
sometimes of bad things generally, used for things like protecting livestock
from evil spells, and (in powdered form) for invisibility.
It is one of the ingredients of Draught of Peace, but Harry forgot to add it to his potion (OP12).
ingredients: unknown
Exact effect unknown, but presumably causes hiccups
Malfoy made this in sixth-year Potions for an assignment to make "something amusing", but it was pronounced merely passable (HBP22)
Used in boil-cure potion (see).
Neville had to disembowel a barrel of these for Snape when he got detention after melting his sixth cauldron in Potions (GF14).
See Polyjuice Potion.
See Voldemort's potions.
