I always enjoy going down to the store and purchasing new brushes - it is something shiny and new and it also means I have been doing enough actual painting with the old brushes to wear them out and send them packing.
I have tried many different brushes from a variety of brand names - and I have found the brushes from Citadel to be fairly excellent. They last for a decent amount of time, their bristles are made of Kolinsky sable (except for the drybrush, which has some nylon in it) and they hold the water and paint well. I especially like their detail brushes that allow me to do some nice work in the tight areas. I have found that the Citadel brushes do tend to "fork" which is a problem that leads to occasional frustration but this can be fixed with some work.
Today I picked up three new Citadel brushes - the Fine Detail Brush, the Standard Brush (gotta love that name) and the Small Drybrush. Easily ninety-five percent of my all my painting is done with just these three brushes. They may not the best brushes out there, but I haven't been able to find a suitable replacement yet.