I am a developer and I have recently released my quiz "Ingenify" for the Windows 8 App Store. You can find it here:
Ingenify (Trivia Quiz) app for Windows in the Windows Store
(English version - Windows 8 - all platforms)
The German Android version, which was the version with which I started, has almost 30,000 downloads and an average rating of 4,6 out of 5 stars. Beside this, there are now also versions for Windows Phone and Windows 8 and they are available in German and in English.
I hope some of you will enjoy the app. Most of the questions are challenging, because I tried to skip trivial questions. Also, the very unique feature about the app is that there is a explanation after each question. This explanations gives you details about the questions, the answers, background information, and so on. So, you can really improve you general knowledge through this.
English is not my first language, but I tried to be as good as I can. If you find grammatical or style errors, please help me and let me know, what is wrong.