ALWAYS(1), COMMON(2), UNCOMMON(10), RARE(90), SUPER_RARE(150)
thats what i use but it's relative to the amount of items in each level, ex:
chance = 1 / (rarity_chance * num_items)
so in order to make some items rarer than others (ex whip) we add more items to the table
(yes i know this sucks lol)
i had a discussion about this in this thread where i found some decent answers: http://www.rune-server.org/runescape...e-formula.html
Also, if you want the rare drop table, I just stumbled upon this: http://services.runescape.com/m=rswi...are_Drop_Table