Bend Modifier
The bend modifier allows you to bend any object or sub-selection along an axis through 360 degrees as well as some other things.
Above the bend modifier has been applied to three polygon cubes, bent along the X, Y and Z axis respectively from left to right.
Bend direction can also be adjusted to offset the effect.
Some interesting shapes can be created using a combination of angle, direction and limit attribute values, e.g. a bent cylinder to create a simple pipe.
To create this effect, upper limit has been applied by checking the limit effect box and setting a value for the upper limit attribute. You can see in the viewport where that limit starts, leaving the rest of the cylinder unaffected.
The bend modifier can be used as a "cheap" way to simulate wind on objects in your scene, such as swaying trees.