Shell 95 or Engen 95 (plus OB or Eth depending on which car). If I'm mixing 50/50 eth, I don't really mind which brand goes in, but on 95 map and my S2000 its normally Shell. I don't think there is a real difference between most of the major brands. Their additives all do pretty much the same thing. A lot of placebo effect going on (I suffer from it too LOL)
Interestingly, I have a knock light on my STI that flashes when it hits a certain threshold. Whilst it is nearly impossible to get detonation on Ethanol, when I'm on my 95 map, the only fuel that sets it off is Total which leads me to believe it is inferior to the others. Have noticed this a couple of times when forced to fill at a Total