Warlock and Hunter only -- sorry!
So, we've all seen the Rogue, or Druid who dismounts around you, or off in the distance and stealths. Well, if you're a hunter you could slap hunters mark on them if you're quick enough (However, this will be changing in 1.12)
The easiest way is to just send your pet after them. They'll stealth, and your pet will still be on its way to them. Once your pet gets to them (as if they were not stealthed) he will start attacking.
So, all you have to do is send your pet after the Rogue or Druid, and watch him try to stealth -- only to be eaten! /Roar
Just a useful trick I use for those pesky Rogues!