Either Tormented Demons or Mithril Dragons for their drops mainly. Also there are the godwars bosses too, even more then Armadyl Boss.
Also the abyssal demons because they drop abyssal whips witch sell for at the grand exchang for 1,400,000
The best monster to kill in Runescape would be the King Black Dragon.
Scorpians.
a nobermom
Runescape can be played with no strategy at all. However, if you want to get the most out of your time spent playing, use the best leveling techniques available.
There is a "Demon" at the top of the "Mages Tower"in "Draynor Village" that's excellent for Ranged and Magic training alike.
level 25 experiments are weak but have 100hp giving you 400 exp per kill - located near canfis, morytania.
Moss Giants are ok at dropping them.
Black dragons is the best!
Hill giants.
The best ( but most expensive ) has to be armadyl.
There are many cooking ranges on runescape. The best cooking range on runescape is at Al-Kharid. It is the closest to a bank.
The best in order are:RangedMeleeMagic