There are only two types of nut mentioned in the Bible. What are they?

Genesis 43:11 in the Revised Standard Version mentions both almonds and pistachios.

Their father Israel then told them: "If it must be so, then do this: Put some of the land's best products in your baggage and take them down to the man as gifts: some balm and honey, gum and resin, and pistachios and almonds.

The Hebrew does mention two different types of nuts - "bot'nim" and "sh'kedim". In modern English, the first translates better as peanuts and the second as almonds, but they could be all-inclusive words, as the context would imply (Jacob sends his ten remaining sons to Egypt to try and bribe Joseph with the best fruits of Israel's land).

Two more refs for almonds:

Jeremiah 1v11 and Numbers 17v8.

Pistachio and almond: "Then their father Israel said to them, "If it must be, then do this: Put some of the best products of the land in your bags and take them down to the man as a gift--a little balm and a little honey, some spices and myrrh, some pistachio nuts and almonds." (Genesis 43:11)

http://biblehub.com/genesis/43-11.htm

Some translations mention walnuts: "I went down to the grove of walnut trees and out to the valley to see the new spring growth, to see whether the grapevines had budded or the pomegranates were in bloom." (Song of Solomon 6:11)

http://biblehub.com/songs/6-11.htm