Hi Brenda :) For me: Polarising Filter - because you cannot replicate the same effect with image editing. ND filter - because it is difficult to replicate same effects with motion blur etc. ND Grads - because it is difficult to replicate the same effect. You can take 2 shots & blend but things can move like blowing trees, clouds etc. Everything else is better done in image editing because you have more precise control over the effect.

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html