I've got a few apps that I've purchased on my phone. I will list the ones I think you people may have some use for and a brief description.

FourTrack - simple 4 track recorder with bounce and many other options like audio copy/ paste from other apps. Tbh I have barely used it but it seems worthwhile. I plan to use it quite a bit in the near future.

GuitarTone - Amps, effects, mics, and cabs right on your phone. Again I haven't used this app much but can copy/ paste your recordings from here to FourTrack.

Combustion/ Heartbraker/ Tropical sun drum machines - I have never really messed with drum machines but am mentioning these because they can also be pasted to FourTrack.

My favorite app so far is,
GarageBand.

Most of you are prolly familiar with it but this is kinda what got me back into music. Made some decent interesting beats on it and its just fun to mess around with. I recommend this the most for beginning musicians.

Songsterr+ - Basically for active tabs that play on screen. Pretty cool and also recommend.

There's a pretty good iphone tuning app, I can't remember the name of it though

Bought iRealB for my iPad recently, and feel like it's going to be really handy.

i use TyroTuner for tuning obviously.

guitarwebapp for chords.

I have a couple metronomes, 1 that flashes, and one that works like a traditional metronome.

GuitarToolKit has a tuner, metronome, chords, and scales all together.

db bump

animoog is probably my best ipad app. Really really good. I got it for 99 cents but i think it's a bit more now