USGI MilSurp
Preferably LC, WCC, WRA or RA. (avoid "U" and "TW.")
I prefer the RP and FC myself. The Winchester brass I have been getting lately isn't very good quality.
I am finding RP and Federal quite consistent when sorted for weight. Hornady is good, too, and so is Nosler. Not as good as Lapua or Norma, but then I'm too cheap to pony up what it takes to buy that stuff.
It's just me, but I try to stay away from the military brass as loads can get quite hot before reaching maximum loads due to the thicker brass.