(Sidetip: look here (http://reviewtimes.shinydevelopment.com/) for a useful website showing real stats on current Apple app store approval times.)
The app store approval process is the last step to getting your revolutionary app out there, but it's easy to forget about because it's annoying.
Submitting an app for review and then waiting 5 days just to have it rejected can be bad for business. That's another 5 days you're going to have to wait before your app gets out there to change the world. So, it's might be worth it to go through the extra few steps of making sure your app is 100% ready before you submit it.
However, if you are trying to get the app rejected, below is a list of surefire ways to make that happen based on common/easy mistakes that I've seen:
(I've loosely grouped these into Apple and Windows mistakes, but most apply to both. Google couldn't care less about what you submit, so you're going to have to get really creative to be rejected by them).
Game Center - Forget to Enable It
If you mention that your app uses GameCenter in your description or other metadata, you better make sure this actually works or the app will be rejected. GameCenter has to be enabled in iTunesConnect for the game itself, in the version that you are submitting, and be functional in the app.
Mis-Match Your Icons
The icon you upload to iTunes Connect should be the exact same as the one that is installed with your app on the device. If these are different your app will be rejected.
Infringe on Copyrights!
Based on the apps available in the Windows Store, Microsoft seems to be a lot more lax on this subject. Apple, on the other hand, is very likely to reject your app if it is obviously copying some other intellectual property. Make sure the name, art, and marketing used in your app is original content or risk being rejected.
If your description doesn't accurately describe what your app does (i.e., aims to oversell/is deceptive) then your app will be rejected. The description and screenshots should be truly representative of the app.
An app with an inappropriate age rating will be rejected. Be accurate in what content your app offers when making this rating.
As desperate as Microsoft is to get as many apps as possible, there are some surefire ways to get rejected.
Use Black for Both the Foreground and Background
These colors tell Windows what colors to show in dialogs and the splash screen.
Microsoft will reject your app if it detects that there is too much of a similarity between the specified font and background colors. Make sure one of these colors is dark and the other is light.
Submit an Incomplete App
Microsoft seems to be sticklers for having a finished product, so don't include any thing that insinuates a "more coming soon" attitude. If your description or a page in your app says anything like this then the app will be rejected.
Broken Buttons and Dead Ends - Have Lots
If you use Unity3d or something other multi-platform development tool, it's possible that you will have buttons/features that apply only to certain platforms. Make sure unused buttons are removed entirely (or have a different function) in the Windows version, because any buttons that don't do anything will be grounds for rejection.
Make Sure Your App Crashes
If your app crashes at all it will be rejected. The testers systematically click every button and explore every feature in your app, so make sure you do as well. Test all functionality in the app, especially in ways that don't seem totally obvious to you. If your app connects to the Internet at all test it without connection as well to make sure it at least won't crash.
The approval processes are good for your app because it ensures you are releasing a product of at least a minimal quality, but it is best if you can avoid simple mistakes to make sure it is reviewed and released as soon as possible.