First up is the C451 Small Round Buffer Brush. I've been wanting a dense buffing brush like this. It works well for the price and is very dense and a nice size for blending foundation, although I also find it to be a little rough and can leave streaks if you aren't careful. It can be difficult to clean, but I've found the Beauty Blender Solid Cleaner works wonders with this style of brush, both cleaning and rinsing easily. Overall though, I think I prefer the Real Techniques Expert Face Brush because it is a similar price point but much softer. I've had my eye on the flat top Sigma version also.
Second was the C427 Tapered Duo Fiber Blush because it was recommended by James Vincent. I have found it to be perfect for pigmented blushes (like my Hourglass Ambient Lighting Blush in Radiant Magenta) because it picks up a very small amount of power and can both precisely apply the color and blend it out. Not only is it affordable but it is a very uniquely shaped duo fiber.