Sony Ericsson J108 Cedar - its incredible. BUT it won't do whatsapp. However you get up to a week battery life, it has 3G - and Sony java based feature fones back in the day could do MULTITASKING - no other java fone could do it. I you want something a bit more recent though, you can't go wrong with a Nokia Asha 311. And there you do get access to whatsapp.
