I had to share my love for the Sigma F80 brush. In short it is my absolute must have favourite foundation brush ever. It's amazingly soft, like velvety soft and blends even the most stubborn of foundation into skin flawlessly, seamlessly and beautifully. I can't recommend it enough. If you want skin that looks airbrushed to perfection with minimal effort then you must buy one! I bought mine from here, it came really quickly in the post and was packaged really well.
Mine is presently covered in foundation and was proving a little hard to photograph (camera flash + silver brush head bit = massive glare!) so I borrowed this photo from good ol' Google.
There are so many reviews and tutorials out there on this brush so I really don't see the need for me to go into it anymore. But I really cannot vouch for it enough, if you use liquid foundation then you neeeed one of these in your life!
What do you use to apply foundation? Have you tried the Sigma F80?