First, heyZap, because it's for games & you can have all your games in one place, they give you badges & stuff & you can add friends. My favorite game is BubbleBreak. I have an android though so not 100% sure Bubble Break's available on iPhone but heyZap is. It has taken the place of answering questions on Answers for me because it's More fun to play games & chat with my contacts on heyZap.