ABS1, blindspot assist, gear indicator (just saves me a lap or two learning a new car on a track, before I ignore it completely, can't watch those little numbers while still hitting my braking points, apexes, and avoiding others).
I use a G27, so simulation/FFB 5/no power steering also comes into play. I use the same setting with the DS3 as well.
For myself, and the half dozen GT-proficient friends of mine I've played with in person, we've all been notably faster with TCS turned off (once we learned to control the car without TCS, that is). ABS, on the other hand, lowered our average times when put to 0, mostly because of lockups. Sure, we could learn to be more precise and prevent that, but ABS 1 is more fun IMO.
SRF will make some cars faster, but it doesn't feel right. It's like driver's ed when the teacher steps on the brakes and turns the wheel, and I don't like anything besides 100% my own control. Same for active steering.