I've used the Galvanize GRE app and I thought it was incredible. I've also used their Vocab app and that's just as good! Highly recommend both.

Hey you can read through a guideline to discover new apps

I hadn't been a fan of these mobile applications. Though I use Magoosh Flashcards, my apex suggestion for GRE vocab preparation would be a web application called "Membean".

Pros:
I) The language engine behind this website is designed especially for keeping track of your progress.
II) Review after each word
III) Quizzes on session based not on a timely basis. Each question in a quiz is time-based.
IV) Has Synonyms and antonyms
V) Has etymology.
VI) Represents pictures for your crystal clear remembrance.
VII) Word Constellation - Has a nexus of synonyms and antonyms to help with your grasp.
VIII) Context-based studying paragraph and answering the context question to start with for every word.
IX) Word theater- A video section to understand how to make use of any particular word in the real world, depicting scenes or acts from plays and movies (or) dialogue conversations.

Cons:
I) Require Internet Connection
II) Not a free-to-use source.