Reeder 3, an app for reading and sharing news stories
Bear, an app for writing, note-taking, coding, and sketching
Instapaper, an app for saving and reading news stories either online or offline
Twitterrific 5, a highly customizable Twitter client
next slide will load in 15 secondsSkip AdSkip AdDrafts 5, an app for writing, editing, and sharing text
Calzy 3, a calculator app that can store and sync past calculations
Just Press Record, an app for recording and transcribing audio into text
Speedtest by Ookla, an app that can test your internet connection speed and consistency
Wikipedia, the free online encyclopedia
next slide will load in 15 secondsSkip AdSkip AdOvercast, an app for searching, downloading, and playing podcasts
Polarr Photo Editor, an app for enhancing, filtering, and editing photos
Apollo for Reddit, a customizable app for browsing and enjoying Reddit
Feedly, an app for organizing blogs, publications, YouTube channels, and other sources of news you like
Anybuffer, an app for storing links, images, documents, and text to re-share later, whenever you need it
next slide will load in 15 secondsSkip AdSkip AdFiery Feeds: RSS Reader, an app for following the news and digging deeper into their sources
Grocery - Smart Grocery List, an app for sorting and marking off items you need to buy
In addition to the apps Apple listed, here are a few other notable iPhone apps with dark or "pure black" modes:
And if you're ever looking for pure-black wallpapers for your OLED iPhone X, I highly recommend the "AmoledBackgrounds" subreddit.
Just click on the link above, and browse and download away.
I recommend browsing this subreddit while you're on your phone, so you can quickly save these photos and try them out as wallpapers. I'd also recommend sorting the site by "Top," either by month or all-time, to see the very best OLED wallpapers ever posted to the subreddit.
(You get bonus points if you're using the Apollo app for Reddit, which has a pure-black mode, to browse the AmoledBackgrounds subreddit.)