Torn between my top three:
Bortz from Houseki no Kuni (one of my favorite character archetypes):

Kirika from Noir (always doing something interesting, great character arc; 'adorable hyper-competent child assassin' who actually comes off as a sweet impressionable kid rather than an obnoxious plot device)

Maria from Symphogear (shameless crush):

I'm also a huge Cell fan, despite not really following Dragon Ball at all since I was a kid. ^^; Perfect Cell is an S+++ design; seeing him was one of those moments that changed my brain chemistry as a young artist. Plus, he has a fun personality on top of that~
And if we're gonna include characters I know almost nothing about, Killua from Hunter X Hunter, Dabi from MHA, and Gaara from Naruto are also top-tier Best Boys for me; always happy to see them pop up on my Twitter feed. ^^ Their designs are great, and the little I do know about them is very intriguing.