Shoot, I was looking for my personal favorite [0] but it isn't in the list: send a few hundred rockets loaded with thin sheets of aluminum foil to the Sun-Earth L1 Lagrange point, and unroll them in space as a sun shield.
It is crazy enough to be exciting yet practical enough to potentially be within reach given recent technological developments and – perhaps best of all – very easily reversible!
[0]: https://www.sciencedirect.com/science/article/abs/pii/S00945...