I had the idea recently to create a wood surface with a spiral grain by using a laser cutter to cut slivers of wood that could be arranged into a circle. If each sliver has the grain pointed slightly inward toward the center of the circle, then the overall grain effect will be a spiral.
It worked out rather well on zebrawood:
Some others I made out of cherry... the spiral feel is much more subtle.
- Laser-cut Christmas presents - Wood with spiral grain