What is the most unified functional model of the hippocampus? There are many different incremental models of the hippocampus and it's role in learning as shown by a quick search. However, have there been any efforts to combine these various models into a single unified functional model?
I myself have not come across a complete end-to-end hippocampal model, but I would imagine that such an implementation would be quite broad in scope. Edmund Rolls has some nice papers on the hippocampus, one of which is a particularly informative and recent review: 

Kesner RP, and Rolls ET. A computational theory of hippocampal function, and tests of the theory: New developments. Neuroscience and Biobehavioral Reviews 48 (2015) 92-147 PDF here (Second page missing?)

I'll be very interested to read other answers to your question.