Scariest ghosts in fiction

The heart in Tell Tale Heart

Miss Jessel and Peter Quint from The Turn of the Screw

The Overlook in The Shining

The cat/kid hybrid from The Grudge & Ju-on

The mother from The Grudge & Ju-on
(I can make the sound she does and scare the sh*t out of my hubby - super fun.)

Sadako from The Ring

The little girl from The Sixth Sense

The twin girls from The Shining

The slit mouthed woman from Carved or A Slit Mouthed Woman

The sack wearing child from The Orphanage

Best under sea dwelling characters in fiction

Captain Nemo from Twenty Thousand Leagues Under the Sea

The white whale in Moby Dick

The Kraken from mythology and various stories

The shark Jaws from Jaws

The despair squid (mostly spoken about) from Red Dwarf

Mermaids from mythology and various stories

Homer's sirens

Hydra from mythology and various stories

Tritons from mythology and various stories

Leviathan from mythology and various stories

H. P. Lovecraft's Cthulhu Mythos creatures

Giant octopus from It Came From Beneath The Sea

Godzilla (and related kaiju) from the Godzilla series

Nabooian sea monsters in Star Wars Episode I: The Phantom Menace

Ichthyosaur and plesiosaur in A Journey to the Center of the Earth

Willy the killer whale from Free Willy

Sebastian the Crab from Little Mermaid

Poseidon from mythology and various stories

Flipper from Flipper

Davy Jones from Pirates of the Caribbean

Titanosaurus from the Godzilla series

Black Spot siren from Doctor Who

The Sea Devils, the aquatic cousins of the Silurians, from Doctor Who

The Sanctuary's Big Bertha

Honourable mention:

Sharktopus from Sharktopus

Best carnivorous plants in fiction

Audrey Jr.

From the 1960 film The Little Shop of Horrors.

Audrey Jr. was renamed Audrey II in the 1982 musical and a 1986 musical film Little Shop of Horrors.

Triffids

From the 1951 novel The Day of the Triffids by John Wyndham.

Triffids have also appeared in a 1960 BBC radio series, a 1962 film, a 1981 BBC TV series and a 2001 sequel novel The Night of the Triffids by Simon Clark. Amongst other things.

Krynoid

From the Doctor Who The Seeds of Doom episode.

Adele

From the 1977 film Adele Hasn't Had Her Dinner Yet by Oldřich Lipský.

Cleopatra

From The Addams Family series.

Deathbottle

From the documentary film The Future Is Wild.

Grippers

From the Deltora Quest series by Emily Rodda.

They resemble toothed mouths growing in the ground, and are covered with cabbage like leaves which open up to let prey fall in when stepped on.

Lashers

From World of Warcraft.

Rytt

A vine-like plant from the novel War Against the Rull by A. E. van Vogt

By Cambium: posted at Digital Art / Drawings / Fanart

Snargaluff

From Harry Potter and the Half-Blood Prince.

A dangerous man-eating carnivorous plant, deceptively taking shape of a dead tree stump when in passive condition; shoots out thorny vines to catch their prey.

Best fictional trees

The White Tree of Gondor, Fangorn forest and the Ents tree herders from J. R. R. Tolkien's The Lord of the Rings

Magical Faraway Tree from Enid Blyton's The Magical Faraway Tree

Jade from Dr Who

Tree of Souls from Avatar

The Home Tree from Avatar

The Kite-Eating Tree from Peanuts

Fighting Trees from L. Frank Baum's The Wizard of Oz

The Giving Tree from Shel Silverstein's The Giving Tree

Great Deku Tree from The Legend of Zelda: Ocarina of Time

The Menoa Tree from Christopher Paolini's Inheritance Cycle

The Truff-u-la Tree from The Lorax by Dr. Seuss

The Whomping Willow from JK Rowling's Harry Potter and the Chamber of Secrets