Mainly TDWaterhouse at the moment but only because of the somewhat unique way they price SPX options commission and the fact I'm trading mostly those these days. Not necessarily the best broker if you're doing anything else, but it is refreshing after IB to get an intelligent person with securities industry knowledge on the phone 100% of the time, even more refreshing to only have to call them a couple times a year because they don't do any unexpected or just plain wrong shit like IB does all the time.