Anor Londo, Ornstein and Smough. It's easiest to kill Ornstein first. That boss fight is the best! I had to backtrack and prepare a little more to fight them though. If you want to get back into it, I suggest taking your time, and before going into Sen's Funhouse go into the catacombs to kill pinwheel and get the Rite of Kindling so you have 20 estus flasks for the Anor Londo boss fight.