
There is a big red warning in your chat box when you receive the drop, even if you have filter off, so no need to check every drop.
Banshees: You can't use cannon in slayer tower but in Pollnivneach dungeon (down the well in the middle of town) you can, and they drop so much pure essence that it pretty much pays for the cannonballs if you pick it all up. It's the main room in the dungeon so just go in and run North, I set up cannon on the middle west side of the room and just left them to it. Used melee for this also. Don't forget slayer helm
Earth Warriors: Used a zammy spear and steel titan in the chaos tunnels. Luckily got this one pretty quickly as this place is horrible and they spread out all over the place. Would try cannoning in the edgeville wildy dungeon but I'm too wimpy. There is a good map of the portals in chaos tunnels on here
Giants: in Edgeville Dungeon, run down to the most southern part and go into the resource dungeon (can also get there using the brass key and going into the house west of Cooks Guild) set up cannon and put auto retaliate/momentum on. Easy

Goblins: I tried a couple of places for these. In the Security Stronghold there are a few goblins in the room one south of entrance but I think the goblins east of Lumbridge castle by the river are more kills per hour. Again set up cannon and you can AFK these
Ghouls: South of the slayer tower. Cannoned these with melee but could maybe use chinchompas? Not tried
Hobgoblins: Tried cannoning in the dungeon under Tree Gnome Village (there's a trap door just outside the broken fence) there is a key in a box in the eastern room and the hobgoblins are in the western room. There are 7 of them, and they respawn fast enough that you're not really waiting around much BUT - and I don't know why I didn't try this sooner - When I went to the hobgoblin mine in lvl 46 wild (just south of lava maze) I killed a few with chinchompas and got the scroll within 15 mins. Only took 5k chins and black dhide into wild so I wasn't risking much. And used the 2400+ world to minimize chances of being pked. Wish I had done this sooner!
Jogres: Use fairy ring code DKP and run south, set up cannon to the north of the glider
Mummies: I killed these at Ullek, in the desert. From sophanem running east, you go over the little sandbag bit and run past the agil pyramid east, then up the rope and there are about 6 mummies as soon as you get up there. I cannoned these and alched the rune drops, which probably made back about half the money I spent on cballs as there are a lot of rune drops.
Skeletons: Used chinchompas in lumbridge catacombs. The catacombs are in lumbridge graveyard, so you go down the stairs and then down the next set of stairs and just keep running through the tunnel until you get to the skeleton room. As they are packed in together, you usually kill 3-4 at once and they are pretty much 1 hittable most of the time. So this is cheaper, faster and more effective than cannon... Win win!! Wish I thought of this sooner. Could maybe use for goblins as well but works best on the low levels that are confined in a small space
Zombies: If you go over the ledge from mummies, and run north into the big open space filled with skeletons, there is a little room full of dried zombies to the east. Set up cannon here. I wouldn't recommend killing skeles here as they are too spread out to kill with cannon effectively.
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Aberrant Spectres: Again got on a slayer task years ago, but there are some which you can cannon in Pollnivneach dungeon but don't forget slayer helm!
Imps/Lessers: Can't comment on this as I got both of these ages ago, but I have heard that there is a resource dungeon in karamja dungeon where you can kill both
Good luck all Champion Scroll Hunters!!! Please ask if you have any trouble finding any because of my dodgy directions ;)