You only really have three choices, a 66, a totem, or a 36. You could break the mold and go with something fancy, ie. magura, but I think you'd be better off going the more common route. Out of the three mentioned I'd go with a 66, but only because I've seen a guy run full-on DH runs w/out a front break on his bottlerocket, and he was riding a 66, not that it matters.
Maniout Travis, like a 150mm if you don't want the full travel of a Travis instinct SP?.
Iv got a bottle rocket, and have a Travis 150 on mine, it matches perfectly with the DHX 5.0 in the rear, making the bike feel very stable because the suspension front and back is even.