(If I have a little lattitutde and can choose a grass) I'll take bamboo. It does everything that you could want from a tree.
- You can eat it (pith and shoots)
- You can carry huge stems (very light)
- It makes great structural material (bridges, scaffolding)
- You can quickly make shelters from it
- You can steam bend it
- It floats, maintains integrity and doesn't waterlog
- Buckets, cups and bowls are easy
- Pipes are easy
- You can use the fibres for string
- You can burn it
- You can bend it
- You can chop it easily
- It grows back quickly
- It's plentiful
The only drawback is that once, in every few decases, it flowers. But that doesn't really affect anyone badly but the pandas.
If you're a stickler, and force me to name a real tree, I'll go with the Banyan. It's not good for the above reasons, but it's magnificent and some of the big old trees have seen more history than many human lifetimes.