These games are addictive as fugg, and all you need is your phone which is great.

Clash of Clans:
http://supercell.com/en/games/clashofclans/


Boom Beach:
http://www.playboombeach.com/


In my opinion, Boom Beach is a lot better. Clash of Clans upgrade costs are outrageous. The game is generally geared to get you to buy gems. I heard this game is making 2 million dollars per day.

Boom Beach is not dependent on Gems and you can get far using your brains. It's all about strategy and using the right troops for the job. I have consistently taken stronger bases using good strategy and planning. It's really fun.