I've dedicated several articles (last one HERE) to nPlayer, an excellent multimedia player with unique multi-subtitle capabilities (AppStore link; $2.99 for Universal version).
Back then, the biggest problem with the player was its relatively slow H.264 decoder – top players like AVPlayer(HD), It's Playing, or yaPlayer, have all had much better decoders. Because of that, in the past I couldn't really recommend the player as a generic player for most purposes.
Fortunately, as opposed to many other players' update statements (see the above AppStore update screenshot – click for the enlargened version), the developers' claiming to have fixed this issue has turned out to be true: now, the playback speed is as good as that of the top players.
Taking into account that the player is indeed feature-packed, I can only recommend it (unless you need AC-3 audio support). It's well worth the price.
A more detailed pros / cons list (again, due to time / space constraints, I can't explain the background of all these bullets. I've dedicated a full tutorial / roundup to almost all of them. Please read my previous articles for more info on why, say, gesture-based fast forwarding / rewinding can greatly speed up seeking in a video or what one needs to know about playing back audio-only files.)
- the two biggest problems (low-quality/speed H.264 video decoder and buggy MKV subtitle rendering) of version 1.4 have been fixed. Now, A6(X)-based iDevices (iPhone 5, iPad 4) play back even 10 Mbps 1080p H.264 streams (like the Monsters test video) in software without really annoying stuttering or frame drops. (Unfortunately, earlier models, even including the A5(X)-based iPhone 4S and iPad 3/iPad mini, can't do the same – they heavily drop frames and get the video and audio desynched after a while. With them, 720p is the maximum software-playable H.264 resolution.)
- hardware-accelerated, flawless MKV playback (added in version 1.4)
- support for video flipping (both horizontal and vertical) – few apps do the same (AVPlayer(HD) does – see its Tools menu)
- DTS audio support
- WMA (including Pro), WV, FLAC, WAV, Ogg Audio and Ape audio support; plays them back in background by default (you can enable the same for the audio track of videos in Settings > Videos > Plays In Background). Note that Ogg Audio and Ape streaming isn't supported, only local playback.
- dedicated fast forwarding / rewinding icons are large and their skipping interval can be independently(!) set between 5 and 300 secs in Settings > Fast Forward and Settings > Fast Backward
- access to both the iPod library and camera roll
- excellent (M)TS support ((European) DVB TS-wise, properly switches between 16:9 and 4:3; handles all subtitle and audio tracks and scrubbing.) Of course it won't play AC3 audio in original AVCHD MTS files or US DVB broadcasts.
- intelligent screen filling (not just “dumb” cropping zoom)
- flawless wired (HDMI / VGA) TV output, also with hardware-accelerated MKV files. (Note that some kinds of videos become choppy when played back via wired connections; for example, all my Standard Definition DVB TS test files. When not output to a TV, they're played back flawlessly on the same device, on the screen.)
- native (non-mirroring) AirPlay is supported for native iOS containers (all the other files can be played back in mirroring mode – with, of course, limited throughput and stuttering). For MKV files, playback is suffering from the same problem as with other “behind-the-curtains” MKV remuxers: plays about 10 seconds, then stops, loads the the next 10 seconds and restarts playing and so on. That is, MKV files can only be played in AirPlay mirroring mode (with its inherent, above-listed problems).
- good streaming support: FTP, UPnP, WebDAV / HTTP. (No SMB, though.) (Also see my UPnP bible for more info on its excellent UPnP support. Unfortunately, there is still no download support for UPnP in version 1.7. Also note that my audio streaming tests (see my posts in THIS on SBM audio streaming and background playback) worked just great.)
- speedup / slowdown works with non-hardware-assisted playback too (useful with, say, podcasts).
- screen gestures configurable. For example, you can easily enable gesture-based fast forwarding / rewinding by overriding the default “Seek” setting by “Forward/Backward” in Settings > One Finger Gestures > Drag Horizontally. Then, it'll use the custom settings you set in Settings > Fast Forward / Backward (see above). Excellent!
- while it can zoom into videos (by selecting “Original size” in the zoom menu), you can't scroll around the zoomed video, unlike in It's Playing.
- no AC3
- still no VobSub support during hardware-assisted playback (see the section titled “Unfortunately” in my last nPlayer-specific article)