200 Items Or Less: Night Of The Living Dead (1968)
A few thoughts: Not only one of the most important horror movies ever made, but one of the most important movies ever made, period. Sadly, even with masterpieces, there are some chinks in the armor. With this one, it comes down to the characters. Apart from the lead, there isn't a single intelligent or rational person in the entire cast, and frankly it becomes incredibly annoying. I hate people as much as the next guy (probably even more), but this makes me hate people far beyond the normal levels. I don't really need to go into how dark and claustrophobic this movie is, and how it ushered in a new wave of horror, but suffice it to say this movie's influence can still be felt almost 50 years later. The ending is one of the most frustrating in film history, but that only assures you'll never forget it. I can't say it's totally flawless (like I said before, the characters mostly suck), but the frustration our lead feels only adds to the doomed tone of the rest of it. Not even my nitpicking and pessimism can prevent me from considering it one of the greats; this is an absolute classic that still holds up today.
Who would I recommend it to? Anyone who cares about horror movies should watch it right away -- assuming they somehow haven't already.