Now to the tip: Obsidium Skeleton Keys. I had made a few of these when skilling up BS on my rogue and forgot about them. Then figured I would try to sell them and to my surprise, after a few clever barks, they sold like hotcakes. Unfortunately, the price of obsidium ore/bars has been prohibitive to them recently for me, but it dropped enough tonight that I put up a few more for 20g each. Two folded obsidium makes two keys, so that's eight ore per key. I picked up the ore for roughly 1g 50s each, which means eight cost me 12g. If the keys sell at 20g, that's 8g profit per key. Not too shabby, hopefully ore stays that low, as I'm currently the only person on my server making them.
Some of the ads I've used to sell them are: (I should note that my ads get a bit cheeky at times, I have quite a following in /2 on my server to see what I'll come up with, but that's a post for another time.)
"Tired of looking for a rogue to open that lockbox that you just KNOW has a purple in it? Why wait?! Head to your local AH and pick up some Obsidium Skeleton Keys! No BS skill required!"
"Screw rogues and their lock picks! Your local AH is now stocked with Obsidium Skeleton Keys for all of your lockbox opening needs! No BS skill required!" (This one is usually followed by "Just kidding rogues, I love you all! Buy my stuff!")
And one of my personal favorites that due to a whisper I received I know led directly to the sale of ten keys:
"Can't find a rogue to open those lockboxes clogging up your bags? Head to the AH and buy Obsidium Skeleton Keys now! No BS skill required! To use them anyway, selling them requires some BS skills...."