The Blackberry Android phone, called PRIV, may be the most secure Android phone.
http://blogs.blackberry.com/2016/03/beating-expectations-android-security-patching-for-priv/
Black Phone 2 might be another alternative, though it is more for data privacy, it may have good protection from malware as well.
http://www.engadget.com/2015/09/28/blackphone-2-on-sale-north-america/