I think Slayer is my favourite to train. I actually enjoy combat thoroughly, so I don't peek at my XP as much and therefore it's a great skill to train when I don't have a ton of time to play - I can log in and complete 1 or 2 tasks and still feel like I made a little progress in the skill 
My second favourite is Farming! This is actually funny and ironic, because as early as 6 months ago I absolutely HATED that skill. I never trained it back when it was released and I quit shortly after, and upon returning to the game last year I neglected farming for a good 8 months or so because I "didn't know how." Finally a good buddy of mine took me out and showed me how to do some farm runs, and it has become such a relaxing & easy skill to train. Not to mention I've made loads of $$ off it, and I farmed enough herbs over time to get myself 99 herblore.
My second favourite is Farming! This is actually funny and ironic, because as early as 6 months ago I absolutely HATED that skill. I never trained it back when it was released and I quit shortly after, and upon returning to the game last year I neglected farming for a good 8 months or so because I "didn't know how." Finally a good buddy of mine took me out and showed me how to do some farm runs, and it has become such a relaxing & easy skill to train. Not to mention I've made loads of $$ off it, and I farmed enough herbs over time to get myself 99 herblore.



