I have UV, circular polarizers, center spot, soft focus (coloured, and non coloured), star, cross, nebula, close up (+1, +2, +4), colour gradients (red, blue, brown, grey), and colour contrast (yellow, orange, red, green, light blue, dark blue). (All are Hoya or Stiffen)
Roughly 30 filters for all of my lenses and flashes. UV, polarizer, and nebula filters get the most use.