If you've never used Swiftkey, you should give it a try: it's a smart keyboard which uses some crazy intelligent algorithms not just to predict what word you're typing, but what word you're going to type next. It's spooky. Just don't, whatever you do, lend your phone to a friend.
Because SwiftKey learns from what you've typed in the past, in messages, Facebook, Twitter — everything. That means it's been reading your confessions, tracking your romantic encounters and learning what gets you off. So when a friend starts typing something on your phone, well... they might be in for a surprise. [xkcd]