As a reminder, the first sentences here are being judged as first sentences, using my patented HEITSIBPMFTSIATRAEMTCR ("how effective is this sentence in both preparing me for the story I'm about to read, and encouraging me to continue reading") scale. On that scale, a five equates roughly to "immediately evokes a specific tone, prepares the reader for the rest of the story, and encourages me to continue reading," a one is "makes me less likely to continue reading," and a three is "a perfectly adequate first sentence, which neither inspires great excitement or great dread." For each story, I'll give the title with a link to my review of it, and the star rating I initially gave that story. Tally ho!
The Appledash Project, 3 stars
The first sentence: The run through the Whitetail Woods was exhilarating.
Thoughts: This is pretty much my definition of a "fine" first sentence. It's not terribly memorable, nor all that interesting on its own, but it sets the location and character mood right away without feeling like it's forcing anything in for the benefit of the reader. That's a rock-solid three on my scale; a good start to the story without necessarily standing out as a brilliant first sentence per se.
Cracked Beauty, 2 stars
The first sentence: “Now be VERY careful with this,” said Heavy Lifter.
Thoughts: This first line doesn't give me much to go off of, but starting with dialogue is a perfectly fine choice, and if Heavy Lifter's first line doesn't set up much by itself, it's fair to say that it does nicely reinforce the cover art and story description. The double-space typo before Heavy's name and the lack of a comma after the first word both are minor things (the latter could be argued to be a deliberate attempt to show his inflection, while the latter's a clear mistake but... well, an extra space isn't exactly the end of the world), but it's going to combine with the lack of impact to put me at a two for this sentence.
The Writing on the Wall, 4 stars
The first sentence: The pyramid's perfect geometry stood sharp against the Iblis Desert's smooth curves.
Thoughts: This is a very solid first sentence. A juxtaposition is always a good way to begin, since it invites the reader to imagine the contrasting elements, and the specific phrasing ("perfect geometry" vs. "smooth curves"), coupled with the iconic nature of a desert pyramid, makes for a strong visual. Even though it doesn't tell us much beyond setting, this is still a four from me.
The Elements of Harmony and the Savior of Worlds, 1 star
The first sentence: It had been a rather long day for Princess Celestia.
Thoughts: For a comic or semi-comic story, I'd like this more; the "rather" gives it a nice whiff of understatement, which could be exploited in the follow-up sentence(s) for humorous effect. Here, though, the "rather" feels misplaced; presumably it's to show that this isn't on the level of some of her worse days (you know, like when she banished her own sister for a thousand years? That was probably a rough one), but as an attempt to show that Celestia's tired and droopy, it's surprisingly misleading despite being 100% technically correct. It does introduce our focus character and doesn't do anything to frighten me off, but it doesn't tell us much more and is rather misleading in terms of tone. On balance, I'll go two stars.
Words Failed Her, 3 stars
The first sentence: Twilight Sparkle's eyes flashed back and forth across the page, eagerly devouring the words.
Thoughts: This does give us a bit of character and setting, and does it in a way that's aesthetically pleasing enough. My only issue with it is that it doesn't really tell us anything about Twilight's mood or circumstances beyond the fact that she's reading; anyone who has even a passing familiarity with the show (i.e. anyone reading this fanfic, presumably) already knows that Twilight loves to read, so this sentence isn't really covering any new ground. Still a three for being a fine but unmemorable first sentence, but a rather weak three.
Believing Stories, 2 stars
The first sentence: The sun woke up before she did that day.
Thoughts: I may not have loved this story, but I love this first sentence. By itself, it's evocative while frustratingly vague. In the context of a story about Celestia, it immediately raises a whole host of questions that demand further reading, and the delightfully nonstandard personification makes this very memorable. I'm breaking out the five stars for this one.
One in a Million, 2 stars
The first sentence: The two fillies trotting along with me kept me going; Both Apple Bloom and Sweetie Belle already had their cutie marks.
Thoughts: Although it introduces the characters, at least, this doesn't impress me as a first sentence. Extraneous capitalization, a seeming non-sequitur between the two clauses, no real hint of tone or purpose... this is a one-star for me.
A Joke Too Far, 1 star
The first sentence: Cadance struggled to hold down her laughter.
Thoughts: Even if I'd added in the next sentence ("She bit her bottom lip, her cheeks puffing out as she tried desperately not to lose control in front of her beloved Auntie Celestia and newly-returned Aunt Luna"), I feel like there's nothing here except a rehashing of the cover art. I don't learn anything about Cadance (or her aunts, for that matter), the setting, or anything else that wasn't on the cover already. I suppose it's not awful, but at the very least it feels like a redundant note to start on. One star.