Answered[ Edited ]
a flat lay-down brush for really packing on colour and preferably thin enough that you can run it along the lower lash line as well:
examples: MAC 239 brush or the Sephora IT medium shader brush: http://www.sephora.com/browse/product.jhtml?id=P14
A blending brush for blending out harsh lines and softening your eyeshadow in the crease especially:
Examples: MAC 217 (the best in my opinion) or the sephora IT blending brush : http://www.sephora.com/browse/product.jhtml?id=P25
A contour crease brush, especially useful for doing any kind of smokey eye and applying color into the crease.
examples: Revlon contour crease brush ( my fave) or Sephora platinum natural crease brush: http://www.sephora.com/browse/product.jhtml?id=P10
Pencil or dome-shaped brush for smoking out eyeshadow/liner along the lash line, or applying shadow to set on the lower lash line:
Examples: MAC 219, Paula Dorf Smokey lid brush, or Sephora platinum smokey eye brush:
Lastly an angled or non-angled liner brush to use with pot gel eyeliners/ liquids etc. for doing thin lines, kitten flicks etc,
Examples: MAC 209 or MAC 266, Eco-tools slanted liner brush, Sephora platinum angled eyeliner brush or angled liner brush : http://www.sephora.com/browse/product.jhtml?id=P18
Good luck and I hope this helps!!
The main brushes that I use everyday are:
- Blending brush
- Eyebrow brush
- Eyeliner brush
- Crease brush
- Small eyeshadow brush
- Large all-over shadow brush
- Concealer brush
I hope this answers your questions.
I would add to mdlsksweethrt's list a spoolie brush. This is a long skinny brush that you can use to remove clumps of mascara from your eyelashes if you have a problem with your mascara. I like a spoolie better than an eyelash comb because I don't poke myself in the eye with it as much (clumsy, I know!) It separates the eyelashes and smooths the mascara along the length of your lashes.
- a b s o l u t e l y n e c e s s a r y -
Flat eyeshadow brush (sometimes known as a paddle brush) - for applying color and packing it on.
Fluffy blending brush - For blending out edges of color and creating a diffused crease.
Eyeliner brush - For applying color onto the lash lines or even making a defined crease.
- l u x u r i e s -
Pencil brush - for blending out eyeliner or applying soft liner, also for making cut creases.