Just go here:
http://itemdb-rs.runescape.com/top100.ws?list=0&scale=0
You'll want to flip stable stuff, which this list is basically made up of, lol.
Flip coal, yew logs, flax, bowstring, some runes if you can actually buy them low.
I also heard onyx bolts (e), broad bolts, cannonballs, berserker rings, and dragon hatchets worked quite well.
Personally, I've just been doing coal, whips, claws, and different kinds of bones.
I did some yew logs, flax, bowstring, and yew longs, too, but they don't make as much profit, so I stopped at the moment.