The Beauty Blender. My new best friend~ Seriously - I was a bit skeptical but loving all things makeup I had to try it out. It is awesome! Sooo much better than a regular triangular sponge. You just dab dab dab and then blend a bit and voila - no foundation lines and perfect coverage. I'm not totally sold on the need to buy the blender cleaner (you can buy just the blender) but I did purchase it to try out.
It's not cheap but totally worth it IMO.