Appears in: The Day of the Triffids (1962)
Scariest moment: One particularly disruptive triffid crashes through a window and terrorizes a fancy dinner party.
Weakness: Seawater.

Remember that priceless scene in M. Night Shyamalan's awful film The Happening where Mark Wahlberg tries to verbally reason with a plant? Anyone who's seen the 1962 British sci-fi flick The Day of the Triffids should have a pretty good idea how we would've handled that moment, given the chance to rewrite Shyamalan's screenplay: Marky Mark's head would've met the plant's venomous stinger.

Inherently silly, yet somehow efficiently executed, director Steve Sekely's adaptation of author John Wyndham's 1951 novel presents a poisonous plant-form known as the triffid. Which can uproot itself, move around as if it have legs and feet, communicate with other triffids, and murder people with the aforementioned stinger.