Vigilance is a buff that a protection warrior can put on another member of her group or raid. The buffed person takes 3% less damage, and 10% of her threat goes to the tank who provided the buff.
The usual trick is to put Vigilance on one of the dps who is generating the most threat. So everyone benefits, they get to do some more damage before being threat capped, the tank gets to generate some extra threat, it’s all good. So I’m a threat thief, hurrah!
I find that I often tend to put Vigilance on the same person. I try to be aware of which fights are most threat-cautious for different classes, where the ranged guys cut loose vs where melee will be closer to my threat. But my usual Vigilance-buddy is one of our hunters. We have a deal worked out privately — he gets the Vigilance, and I get the misdirects.
It started slowly, like all good relationships. I noticed that his threat was high (and his damage even higher) and stuck Vigilance on him one night. The next week, he hugged me as we gathered together for Ulduar and whispered to me to ask if he could have Vigilance again. I said, ‘How about some misdirects? :P’ and a beautiful friendship was born.
See, most people don’t notice which buffs they’ve been laden with. To find someone who not only notices the Vigilance but appreciates it … well, it makes you feel kind of warm all over. I think he’s a keeper. But I admit it is an odd basis for a relationship.
Welcome to Spinksville! 
Hmmm…. just to be contrary, a Hunter seems like a really poor choice for vigilance: they already have an amazing threat dump.
I would think that the following are all better choices from a min-max “benefit the entire raid” point of view (roughly in this order):
DPS Warrior
Ret Pally
Enhancement Shaman
Boomkin
Elemental Shaman
Mage
I think it can depend really, every raid group will probably have a different set of dps who tend to top meters. And although hunters can feign, it might be that the combo of the extra damage he can do if he doesn’t need to feign plus the extra threat added to the tank ends up being better overall.
Also, dps warriors (sadly) aren’t threatening the tops of any meters since the last patch ;/
Threat issues make me crotchety. I have seen WoW move from a game where dps was a system of bursting and throttling and ripping aggro was considered the sign of a complete noob to a game where dps is considered something to mindlessly spam and if the tank loses aggro s/he’s a noob.
I think currently threat management is a team thing. I hate the fact that to many players it’s seen as a tank job. Dps have many options to manage threat or help tank threat and your raid is gimped if they feel they don’t need to bother.
As tank you should never have to make deals for Tricks of the Trade or misdirect. They are so obviously good that they should permanently be on cooldown. If your hunters and rogues are more inclined to choose a shot that pushes them further up the damage meter than a move that helps the raid win it’s just demoralising.
I have raided as a hunter and except in the first 10 seconds of a pull it’s impossible to rip aggro (even back in the old Wait for 3 sunders days of terrible tank threat). Provided FD is in your rotation. FD sets your threat to zero. It have a 30 sec cooldown which you can glyph down to 25 secs with a minor glyph. It is almost never resisted if you are at range.
If I were still raiding with a Hunter my opening would be Misdirect – 3 big shots which cause tank threat – 4 or 5 other shots – FD – rotation until MD ready – MD – FD. Not only can Hunters set threat to zero every 25 seconds but 3 of their shots will be MD shots not shots that generate Hunter threat.
Having said all that I have seen Hunters rip aggro. When it happens I feel like I’m playing with someone who has only discovered what 3 of their class’s skills do. Demoralising.
Of course possibly the player knows his stuff but is simply more focused on meter whoring than on playing the best moves for the raid. Also demoralising.
Andrew gives a good list of classes who are much more deserving of Vigilance. Another option is to steal some threat off another tank. Sartharion + drakes is a good example of fight where Vigilance on one tank would work well. The Sarth tank has bundles of excess threat and the drake tank needs to generate huge damage quickly. 3% less damage on the Sarth tank is also useful.
Of course WoW is a social game and if you’ve found a way to social engineer a one button macro spammer into using one of his class skills he normally doesn’t bother with then good luck to you. But you really shouldn’t have to.
Stabs: Think calm thoughts. I just thought it was an amusing mini relationship.
Ha ha, sorry.
Think I need a break from tanking for people who are offended by requests to watch Omen.
In our guild 2 prot warriors putting vigilance on each other. -3% damage on both and they just exchange threat.
Each MD properly applied (no DOT ticks, no explosive shot) can generate up to 15000 threat with three crits, but average 8000. Assuming two per minute on average, that’s 267 threat per second. Rogues have it much easier- for 6 seconds, all their attacks (not just 3 shots which can’t include dot ticks or explosive shot) generate agro for the tank.
The main purpose of MD is it establish initial threat at range, but using it periodically is really a very small effect. It certainly doesn’t hurt, but unless your pure DPS classes without threat dumps (like mages) are throttling more than their mana would force them to anyways, it’s probably a waste of time.
3% damage reduction on a clothie: useful.
Stealing threat from high-dps fire mage: very useful.
Regularly reminding my wife that I’m thinking of her: PRICELESS.
Okay, romance aside, I’ll vig the top dps when I want threat, or another tank if I want the regular taunt refreshes.