Larch makes excellent shafts.
If you're interested in keeping it traditional, the most common arrow shafts found on the MR were Aspen (or Poplar, pretty much identical) followed by Birch, and Alder. I love Birch shafts, they're chunky and heavy and very easy to work. I remember doing 12 EWBS Standard arrows from ash, and cutting the nocks to insert the horn strips took FOREVER. Blitzed through a set of Birch though.