This is based of the Dragons (Just all of them) page. Unicorns are less unique than dragons so getting them all won't be hard.
Harry Potter Unicorns[]
Unicorns in Harry Potter are born a pure gold color and become silver at two years old. They grow their horns when they are four and turn white when they are full grown. Their blood, horn, and hair all have magical properties. Their blood is thick and is silver in color. Unicorn blood keeps the drinker alive but curses them for life. Their white horns are an antidote to common poisons and are used in a few potions. Unicorn hair is used as a wand core and in potions. As a wand core, they are hard to use for the Dark Arts and usually aren't very strong.
Gravity Falls Unicorns[]
Unicorns in Gravity Falls are bright colors and speak telepathically. Their blood and tears are liquid rainbows and can kill plants. Their horns can glow, point to the nearest rainbow, and play rave music. They also are able to project heart shapes on to things. The most magical thing about them is their hair, which is a part of some sort of ritual to keep Bill Cipher's magic out of the Mystery Shack.