5. Game of War: Fire Age

Game of War: Fire Age by developer Machine Zone is one of the most high-profile mobile video games out there, in no small part due to an aggressive advertising campaign featuring model Kate Upton, who became a celebrity due to her popular appearances in the Sports Illustrated Swimsuit issue (although she’s since been replaced by Mariah Carey in the game’s commercials).

And Kate Upton herself also appears prominently in the game (or rather a cartoon version of her) enticing players to spend money on microtransactions in order to gain an advantage in the game. While Game of War is free to play, the game’s competitive nature, in which players form alliances and try to take out opposing kingdoms, means many are tempted to spend real dosh in order to accelerate resource collection or troop creation, for instance. And given Game of War’s addictive nature, it is no surprise that it was still on of the most played mobile games in 2015.

Available on: Google Play, App Store.