Although Silicon Valley-based WhatsApp ($1) is more popular in the US, China-based WeChat, a free texting app, blows it right out of the water.
WhatsApp seems outdated compared to WeChat's graphics, user interface, and add-on features. Designed by Tencent, the app provides users not just with free text messaging but also with the ability to send voice texts and video chat.
There are even Instagram-like photo filters so you can tweak photos before sending them, and you can also use a GPS-enabled location sharer that shares where you are on Google maps with your friends, making it great for meeting up.
Another awesome perk to WeChat is the social aspect, including a "moments" section that acts as a Facebook feed. You get to share statuses, songs, pictures, and more with your WeChat contacts. Another win for WeChat is that you can sync with Facebook and find contacts, beyond the contacts in your phone.