From what I have been told, I would vote for Sneferu. I dont remember the exact wording now, but there have been many references to him as being one of the most approachable pharaohs.
There was this one tale where a female rower was willing to show him her distress in loosing a turquoise amulet or jewelry piece of some sort in the nile and he offered to replace it. When she refused, sneferu helped her search for it. You can see here that a lower class woman was not afraid to approach him and ask for help.
For such a class based society I think this is pretty huge
If a king didnt like you, you could theoretically be disposed of (with one swift hit from a mace).