Ice warriors are level 57 NPC's. Ice Warriors are the best for gold charms per hour. They are located in VIA Dungeon Teleport > Ice Dungeon. As well as Dungeon Teleport > Chaos Tunnels.
I use them for charms because they only take a few seconds to kill. If you're going for 99 summoning this is the way to go, you will get 100+ charms per hour.
Bones - 100% Chance.
Gold Charm - 50% Chance.
Green Charm - 1.01% Chance
Crimson Charm - 2.0% Chance.