200 Items Or Less: Creature From The Black Lagoon (1954)
A few thoughts: Often considered the last of the classic Universal monsters, this is a fairly standard monster movie that arrived at the perfect time to help usher in a new wave of creature features. Released the same year as the original Gojira, it's safe to say 1954 was a pretty important year for these kind of movies, and while I have never really loved this movie, its influence on horror can be seen from a mile away. With beautiful underwater cinematography and one hell of an awesome monstrous costume, a good deal of what makes this particular film so good comes from how relatively unique it was for movies of its time. Instead of just being an irradiated slug or a giant turkey or something, this creature is just an alternate man-like evolution and is in ways sympathetic, with the human characters trespassing on its territory leading it to feel threatened. It isn't an all-time horror classic in my eyes, but marks a significant turning point within the genre, and must be regarded as such. Also, it's worth looking into as an early inspiration for Jaws.
Who would I recommend it to? If you've seen the older Universal monster movies it's worth a look, and fans of people-in-monster-costume movies should find plenty to enjoy, as well as horror historians.