My fav grooming things are:
- cowboy magic. I love the stuff. Makes them so shiny and pretty ;)
- grooming blocks for shedding
- furminator as someone else said although I don't own one of my own yet. I have to borrow someone elses ;)
- white spray for socks. I use the bio-groom range for that. I have it in white and black and the foam shine spray stuff
A good range of things like rubber bands, pro-plaits and other stuff like that for prettying them up for shows is good too. Its often hard to get bands that suit horse hair colour unless that are white or black. Chestnut bands are terrible to find. The last lot I got were more pink than chestnut and then the ones before that were normal rubber band colour which really stuck out against my mares mane colour.
That's all I can think of at the moment