Just a quick note this morning.
A lot has been said about threat stats for tanks and I've seen people going so far as to gem and enchant for it. While it's really not necessary in raids at all, it is useful to have a bit of it in dungeons. While you're PuGing your random Heroic and run into that "lol u r bad ur h8 suks lol" Mage who's spamming Pyroblast like it's going out of fashion, having a bit of hit can help.
I found my usual tanking set supplemented with Might of the Ocean and Right Eye of Rajh will get you a good, long way towards getting to that cap, and as you're probably in 350+ gear anyway, you're not going to miss those survival trinkets.
Alternately (or in addition to the trinkets if you're nuts) you can swap in the Retribution Tier Pants instead of your tanking pants - the primary stats stay the same, you get a lot of Mastery and a ton of Hit.
Finally, you can also use one of the Hit trinkets, the tier pants, and go with Magnetite Mirror to get a boost to your Expertise. Left Eye of Rajh isn't bad either if you're desperate, as the agility proc isn't terrible.
And one final note - these trinkets are all DPS trinkets. If the main-spec DPS warrior, paladin, death knight or rogue is rolling on them, pass the roll, as they are all nice-to-have for tanks, but they can be essential for DPS trying to hit their caps. Don't be greedy.
Good luck out there!