Ankous in the Stronghold of Security, level 4. They're good money for their drops, sort of ok for exp. You get somewhere around 40-50k exp an hour depending on what weapon/style you'll be using. If you want purely exp, go fight lesser demons or greater demons, maybe even moss giants. They're all quick easy kills, but their drops aren't the best. I suggest bringing a weapon/shield to use, as guthan's warspear is not a good weapon to train with. Just use it to heal.