well... lately it's been Scirocco. I didn't expect to fall in love with him when I watched Zeta but I really, really, really like him a lot. He's so deliciously smug and arrogant in the best way possible. See, when his plans don't go his way he very smoothly goes "ah, oh well" and starts scheming even harder. And he handles other people with such grace... He can gaslight me any day and I'd thank him for it. Both of his uniforms are pretty sexy too.
If you asked me a few years back it'd be Kotomine Kirei. What I love about him is his struggle to be an ethical person and to find meaning in his life... of course, you see how that goes. I love seeing characters struggle with their innate desires.
This is an odder pick: I also, for a period of time, loved Mephistopheles from F/GO. I don't think a lot of people know this about me but I think clowns/jesters are very cool. I love his wacky/bombastic personality and his flamboyant clothing.
Takeda Akane from Hanachirasu, I couldn't figure out my feelings about him but I realized it's less sexual and more "I highly respect this man and everything that he stands for". Well, he's a little bit amoral, but that's fine. I think the way he lived his life and died was very beautiful, to carry out one desire like that so single-mindedly.