Different types of ND filters

[ALwin]

Apart from the standard ND and graduated ND filters, does anyone find having other types of ND filters useful?

> Color graduated NDs
> Combination graduated NDs
> Reverse graduated NDs


Oh and if you don't mind my asking, what stop ND (standard or graduated) filters do you carry in your bag?

I myself only carry the following:
3-stop and 10-stop standard ND filter
1, 2, 3 stop set of each hard/soft ND graduated filters

Should I consider getting a 5-6 stop standard ND filter along with a set of reverse graduated NDs for landscape work?