I used to think that cherry would make a good peg but since tearing into older buildings I am convinced that the harder woods with rot resistance make the best candidates for pegs. It would be tempting to design pegs to the task with medium hardness woods. Increase the common peg radius in .125 in. increments, calculate cross section area and be amazed by a significant gain of fiber and strength.

The problem with that approach lies in the lack of hardness. Pegs are always in the pinch and most every peg in an old building will bear some compression set and very often plastic deformation. In my area I see mostly oak and black locust pegs, my impression is that the harder locust suffers less damage and rot than oak. I would be very concerned that softer wood than oak will suffer compression set from first draw boring and later from load cycling and moisture cycling. Once compression failure occurs the fiber is forever compromised, and a path to progressive failure is opened.

If you want something different than oak or locust try looking for osage orange or persimmon they have dry specific gravities of .85 and .78 and rot resistance to match locust.