What Music Apps are on Your iPhone?

I've had an iPhone 3G for over two years now, and I really love it.  So what are the keeper Apps on there?  I'll stick to apps somewhat related to music... presented in the order they appear in my phone, rather than anything more scientific:

1. WikiPanion - Simple interface to Wikipedia.  Frankly, this one gets quite frequent use, particularly in conversation or watching TV/movies.  Real handy to find out that in fact that favorite guitarist is much (older/younger) than I thought, etc.
2. Remote - Apple's wireless remote control application for controlling iTunes (etc... I don't yet have iTV) is pretty great.  I use an AirPort Express to stream music from my Mac to my stereo, and it mostly works very well.  And occasionally not well... I haven't yet figured out what causes the interference that messes it up sometimes.
3. Guitar Toolkit - This is a great app containing a very good guitar tuner, as well as interactive chord diagrams.  It's aware of multiple guitar/bass tunings and provides tunings for a number of other stringed/fretted instruments, including Ukuleles and Mandolins.  I paid real $ for this app and it's my favorite tuner application.  I think it's better than the built-in ones on some of my guitars, and seems more accurate than the other iPhone apps I've used (just a gut impression).
4. PolyTune - I had eyed the ads for PolyTune tuners in the guitar magazines, and was intrigued.  This app seems to be $10, though I don't recall paying that much for it at the time.  But maybe I did... cheap compared to buying a pedal to see if I like it.  Overall, I rather do like the PolyTune approach, and will probably buy one of their pedals eventually for playing live.  The idea is that you can strum all your open strings at once and see immediately if any of them are out of tune.  Then playing a single string brings up a traditional tuner interface to fine tune the string.  In the iPhone, I think this app is a decent tuner, but I frankly find the Guitar Toolkit one nicer to work with.  In a pedal, though, muting my electric for a second and checking the tuning of all strings together would be awesome.
   
   
5. Guitarist's Reference HD Free -  I downloaded this one awhile back.  It seems to be an OK chord reference, but I don't ever use it.  Though I never removed it from the iPhone... guess I figure I'll eventually use it to find some chord.  Again, though, I'm more likely to use the Guitar Toolkit instead.  It does provide left/right handed chord setup, which might be useful for lefty players... I noticed that my left-handed daughter had some difficulty with chord diagrams, etc. which are written right-handed.
   
   
6. SPL - This sound pressure level device reports noise level in DB, in a few different types of modes that are unfamiliar to me.  I find it occasionally interesting to understand the background sound level, or how loud some "really loud" noise is.  I haven't compared it to professional devices, but did read review comments on it originally that suggested it was reasonably accurate.
   
   
7. FourTrack - This four-track recording software is simple and it's always in my pocket.   Probably doesn't compare to a dedicated device, but it's very handy for recording a tune that's in my head, whether experimenting on my guitar, or whistling something I want to remember.  I suspect there may be better similar apps out there, but I haven't tried them.   The sound quality on this one is extremely good, given the tiny microphone in the iPhone.  My only beef is that the sound level is very low if the input signal isn't loud.  That is, it's much nicer for recording something I'm playing through an amp, than for recording an acoustic track that I'm playing quietly in my bedroom.  Definitely worth having this or something like it at all times, though.  I have imported recordings from this into GarageBand and been pretty impressed overall.  That said, I rarely record more than one track on it.  I'll note that multiple tracks are exported as separate files (WAV? I can't recall).  They then need to be imported separately and aligned inside the recording software, though I didn't find alignment to be a problem.
   
   
8. Shazam - I use the free version, which is just fine.  This is a great app for recalling the name of a tune or performer from some recorded music playing over the radio.  It often works very well in places with a lot of background noise that I'd have bet would not work at all.  It's useless for archaic music, though, or recordings that are not published [in iTunes, I think].
   
   
9. MiniPiano - I carry this with me always, and yet very seldom play it.  It's a pretty useless sounding thing with only one octave, but serves the purpose on occasion.  I'm sure there are better apps for this out there... I just haven't looked in a long long time.
   
   
10. PremierGuitar - Online magazine reader.  It's free, and frankly I'm kind of impressed with Premier Guitar magazine, which I've only found once in print copy.  Quite a well rounded magazine, and the app lets you see the table of contents of the current issue (or back issues, I think) and access individual articles directly.  No paging through like the online experience of GuitarPlayer... as an app it's nice, and I occasionally pull it up to read in waiting rooms, etc.
    
    
11. Matrix Music Pad - I was looking for something along the lines of the Korg SynthPad product, and found this app.  It's kind of entertaining, but I think is just a toy without much practical value.  Still, it does provide the basis on which an electro-dance track could be built pretty easily.
    
    
12. Moog Filtatron - An analog synth program from Moog, Inc.  I have played with it some... only got it about a month ago.  I had read a complaint on the App Store page about it eating batteries, and I think I have confirmed this in my experience.  I'm running iPhone 3G, which does not support background applications, and yet when this app has been exited, I found my phone battery drained quite quickly. Only after rebooting the phone did it get back to normal battery behavior, so I suspect there's something wonky with this app.   That said, I think this can generate some very cool sounds, which can be exported and integrated into a music project on your computer.  I suspect I will use it to craft some interesting sounds in the coming months.  Yeah, I don't have an analog synth, but would like one, so this is attractive to me.
    
    
13. CraigsPhone - App interface to Craigslist... a good way to pass the time looking at music gear for sale. 

OK, that's plenty for today.  I hope one or two of these are helpful to you.