Whatsapp is great! I use that and Kik a lot to talk to people overseas. I also have a world clock that I really like called Perfect World Clock. It's helpful when I need to text someone overseas and need to know if I'm texting them at like 3am or whatnot.
I use a lot of weird apps, I guess. I do a lot of business-e stuff on my phone, so I use google drive and google translate a lot, as well as the Orbitz app so I can get a general idea of flight costs. Paypal, both my banks apps.
On the game front, I have things like steam and the wow armory. For actual games I have tetris, draw something,