What professions give the largest stat bonuses for a Cataclysm PvP Warrior?
Update for Patch 4.0.6!
Leatherworking is now exactly as good as blacksmithing / enchanting / alchemy / inscription. Pick Jewelcrafting if you need that 1 extra stat, but the rest are totally a wash.
Jewelcrafting can give up to +81 to a primary Stat, whereas enchanting / blacksmithing / inscription etc. only give +80. (Exceedingly minor difference.)
Also worth looking into is Leatherworking, which offers unique arms-slot enchants that are unique in that they provide a primary stat bonus (such as strength) otherwise unobtainable as an enchantment in that slot.
In general, the gathering professions provide less useful benefits than the secondary professions, a possible exception being Mining, which provides health. (Strength is a better damage increaser than both crit rating from skinning or an activated haste+heal from herbalism).
So the bleeding edge optimization would indicate Leatherworking and Jewelcrafting as the best, in terms of pure +stats. Mining / Jewelcrafting is easier to level, and the bonus health from Mining is not wasted during the period before (if) you switch it for leatherworking.
Beginning with Wrath, and developed to completion in Cataclysm, class is largely meaningless when looking at profession bonuses. The core primary stats of Intellect / Spirit / Strength / Agility are usually all available within a single profession (if they're present at all), making class choice largely irrelevant.*
Even Tailoring isn't useless for melee characters, as it provides a +AP cloak enchant (though its proc-based benefit compared to simply passive +strength is debatable)