Noir costume actually. And if they count, Kaine's Scarlet Spider and Miles Ultimate costume as well. But they're not on the list so I pick Symbiote.
I was going to add Miles and Noir, but then it opens it up to every variation of the costume, and thats a lot, so I stuck to Parker's 616
I think I'd have to say either the classic (no armpit webbing- it doesn't really bother me that much, I just prefer the costume without it) or the symbiote costume. Both are really cool, so it's a hard decision. Bag Man is definitely a close third.