Rope

The rope is the material with which you can do most weird things, and lots of shenanigans.

Main use
Ropes are generally used to stabilize a fort, or hang a part of a fort if you attach it to the ceiling (when there is one).

You generally attach some at the back of your fort, when it's leaning too much towards the front, because you built heavy defense. You can also use them to stabilize hanged part of a fort, thus being able to build stable bridges.

Other uses
You can use ropes to make bridges when you need to connect by building down : build a wooden strut, and attach a rope to the platform you're building towards. This allows you to place another strut starting from the previous one and keep doing that.

Ropes are very well known for making T3 weapons. They can sometimes be seen as memes, but sometimes are actually viable.

Some players move their core (Coreswing) from their usual position using ropes, swinging it back so it doesn't take as much splash damage, and is easily defended.

Finally, you can use ropes to make TK (TeamKilling) techniques, in order to kill your teammates.