A stick chair made of a single 2x4x8 and some threaded rod. Turned out great. Kid approved!

Steps:

1. Cut 2x4 in smaller sizes.

2. Rip into 4 equal sections.

3. Drill holes

4. Round over all edges

5. Sand down 

6. Stain/treat wood

7. Thread it all together

8. Hope your kid sits in it!