Steel Drags and Hellhounds for me, the rest are alright

I have personally blocked Irons, Steels and Wyverns because they take too long.

 

Aberrant Spectres - Takes 20 minutes with Cannon.

Abyssal Demons - Awesome XP.

Black Demons - Awesome XP, Cannon + Melee.

Black Dragons - Baby Blacks, quick task.

Blue dragons - Decent XP.

Bloodvelds - Mutated Bloodvelds are the fastest Slayer XP.

Dagannoths - 25 minute tasks cannoning at lighthouse.

Dark Beasts - Awesome XP.

Dust Devils - Decent XP.

Fire giants - Decent XP. Cannon + Melee @ Wildy Dungeon

Gargoyles - Decent XP + Fast but right clicking each one to hammer it is annoying.

Greater Demons - Decent XP + Fast

Hellhounds - Decent XP, Bit slow and ugly drops.

Iron Dragons - Too long.

Kalphites - Decent XP/Cannon + Melee

Living Rock creatures - Awesome XP/Cannon + Melee

Mithril Dragons - Fast task, bad exp.

Nechryaels - Decent XP.

Skeletal wyverns - Too long.

Spiritual Mages - Pretty fast, decent xp, good cash.

Steel Dragons - Too long.

Suqahs - Cannoned a Suqah task in 8 minutes, very fast.

Terror dogs - Takes 15 minutes, paying points for slayer ring lasts 8 terror dog tasks.

TzHaar - Bit too long, decent xp, obby charms are great for level 83.

Warped Tortoises - Decent xp, good cash but using crystal chime is so annoying.

Waterfiends - Good xp, great crims, takes a while and with unicorn you don't need to pray.