Every photographer will have his/her own favourites. A polariser and a red or orange filter often top the list. I use my polariser more than any other single filter (save for UV L41 or Skylight 1B), chiefly for modulating the palette of Velvia. I like strong contrast in B&W (e.g. with Delta 100) so its "pol to the max" or "reddit" for a bog standard effect.
I used a single coated lens for velvia.
For mono carry three yellows 0, 1 and 2 (from Leitz).
uV for sea gulls.