Apple has hit 50 billion app downloads. Many more if you count all the unofficial apps that can be grabbed from Cydia on a jailbroken iPhone. Some of these are infinitely useful and belong in the realm of official status.

Flux:
The brilliance of Flux is you never notice it working, yet it's becomes impossible to live without. As the sun sets, this app adjust the colour temperature of your display to a warmer hue. It's well known that bright white light in the evening causes eye strain and sleep problems. Flux makes using your iDevice at night a lot less stressful on the old peepers.

iFile:
Have a problem with the 16GB iPad's lack of storage? No problem! Just pay $200 more for the 64GB version. What if that's still not enough? Say you have a huge movie and music collection, or you edit a lot of photos and videos on the go. Tough lucks. The iPad is one of the few high end tablets that doesn't officially support removable storage. Even Microsoft's craptastic Surface has a card slot. Thankfully there's iFile. It's a file browser for the iPad but it also lets you use the camera kit and an SD card to store whatever you want. Apple doesn't trust it's users to deeper into iOS's file system. However, it's hard to deny how useful something like this is.

BossPrefs:
Full control of you phone's settings from the notification menu. That's all you really need to know about BossPrefs. Adjust brightness, turn off cellular data and WiFi, or free up memory with one touch. Go in deeper to see memory and disk usage, and your IP address. It eliminated the kludge involved with adjusting basic settings, without using the settings app. Apple will never put a utility like this in the store, since it gives the user too much unsanctioned power. Though it's something that should be integrated into the next iOS.

Got some more jailbreak apps and tweaks you can't live with out, and want to see go official? Post them in the comments.