Hm... There are just SO many different artists, it's close to impossible choosing just one... >_<
I think for solo artists Imma go for Sky-Hi. He's a rapper but his style is super diverse, I'll never ever get tired of him~
And bands... I only add bands to my inner list but I don't usually scratch them, so... Even more difficult!
For the past 2 years I've been especially into SekaOwa and One Ok Rock though :3
SekaOwa are like Vocaloid meets Owl City(How awesome is that) and OOK are just the right mix of rock, pop and interesting lyrics~