I found this out when I was out grinding.
I have a MM hunter, and I use the Master Marksman talent which makes Aimed Shot instant when you have 5 stacks of some debuff, which you get when you do steady shot.
For Aimed shot I use this macro, because I always pull with aimed:
#showtooltip Aimed Shot
/cast Aimed Shot
/petattack
If you use this macro, and get the instant Aimed Shot buff, it wont be instant but you can cast it while running.
Did numerous tries and it always works.
It may not be usefull, but maybe someone can find something to use it for.
Thanks