The highly addictive trivia game QuizUp, formerly an iOS exclusive, is now available for Android on the Google Play Store (where else?). The game's user-interface is the same as the iOS version, so there should be no problem adapting for anyone who has played it before (as I'm sure most of you have).
Upon launching the game for the first time, you're offered three options for signup: Facebook, your Google Account, and traditional email (in case you don't like either option). If you decide to use your Google account to signup, it does take your profile picture and cover photo from your Google + account, so be wary of that. Upon signing up, you might want to head over to your settings and enable "Privacy Mode" - this prevents strangers from seeing your profile. They'll also need your approval before adding you as a friend.
QuizUp later prompts you to connect to Google Play Games, which it uses to keep track of your achievements and list your ranking on leaderboards - in your Google + Circles and publicly (don't worry, if you don't want to use Google Play Games, you can still check these in-game).
As Plain Vanilla Games mentions on their website, QuizUp gives you the opportunity to explore over 400 topics, answer 220 thousand unique questions, and play against 10 million (and counting) fellow gamers. By connecting with other social accounts, you can quickly add friends to QuizUp and challenge them in any category (they don't even have to be online)!
Aside from being a place to learn (and hopefully, win), QuizUp also allows you to use built-in social features to properly show off your bragging rights - in the aforementioned leaderboards, built-in chat, and the topic-specific discussions, where users can well, discuss, about ideas pertaining to the topic at hand. After reaching level 15 in a category, users can apply to become a contributor (the people who make the thousands of questions we answer) on the QuizUp website.
Well, what are you waiting for? Head over to the Google Play Store and download QuizUp!