Back before they took out the Raptor mount boss I helped a buddy kill him each (I think) three days? The lockout might have been a week I can't remember. Anywho. One week I told him I'm going to do it on my own if he doesn't mind which he said go for it. After killing the boss on my first try solo (note i've only did it for about 3 boss kills with him) there sat the raptor mount on his body. I linked it in guild chat with saying "Is this what you are after?" He told me I was bullshitting him until I clicked it and got the achieve.
Another good story of mine is a friend couldn't solo TK for her life. Me and the same buddy agreed to help her for Ashes for a fee. She said she would pay us EACH 100k gold if the mount drop and we passed. I'm not a huge mount collector and neither is my buddy being broke this was a great chance. Week one: no luck week two: Bam 100k gold for the both of us and a mount for her. Was a good feeling. We joked the first week after not seeing it that we just got ourselves into months of farming this damn boss for someone.