This thread has been inspired because of a game known as Montowers. Basically, it was free just a couple days ago, but now you have to pay for it. Granted, it's only $0.99 and it's quite the in-depth game, but you do have to pay for it now, versus when it was free just a few days ago. So, what games have you noticed charge now, but used to be free? I'm listing this one:

Montowers: App Store - MonTowers ~Legend of Summoners~