Personally, when my raid hits a roadblock against some boss, I equip my good luck charm. I've used it in all of our "big" firsts: Lady Vashj, Kael'thas, and Archimonde have all fallen to the might of the Shard of the Fallen Star. I'm sure my raidmates are tired of seeing that thing in the middle of an epic battle, but it works, so don't knock it! Besides, a giant meteor falling out of the sky and hitting Archimonde is totally awesome.
I've seen mages equipping their fishing hats for specific bosses and warlocks summoning their favorite demon, no matter how useless it is, when they're in need of a little good luck. What about you guys? Do you do anything special to shed the bad mojo?