Buy these. They look like a spinning firework on the ground, and does a nice sound, I find it pretty cool. Many stacks, you can make a lvl 1 alt for that, buy 16 slot bags and fill it all up with them.
Wait up a month or two.
Sell them all for a big profit (30g/stack? set your own price). They may not sell at first, but you can drop a few off in middle of IF/Orgrimmar/Dalaran and make an attracting ad in trade. I'm 100% sure MANY people will ask you like:
"where have you got them etc I want to buy!"
I never seen it myself until some guy shooted it off in IF, many people gathered around him (today). Harvest Festival gives no achievs or title whatsoever, so noone is bothered with it and continiues doing the Brewfest stuff.
And even if you don't sell much, it's nothing lost... 72 stacks of the 95c firework cost like ~13.6 gold, and if you even sell one stack for 30g it's covered ^^.
I know it's pretty much common sense, but I'm sure not many people know even that thing exists and what could it be used for.