Chuggy

Try Rock Crabs or Kalphites. But remember, if you are going to do Kalphites, bring a few anti-poison potions unless you are killing the weakest ones (Kalphite workers). Rock crabs are mostly packed with lots of people killing them and it's also a multi-combat area which makes it an excellent place to train with your cannon. If you are looking for cash rather than XP, I would try black demons or hellhounds (cash from clues). Hellhounds also drop a fair amount of gold charms. Good luck :)