It's a shame I've only just discovered Wagakki Band.
I also dabble in the work of SID and the GazettE, Chiaki Ishikawa, Eri Kitamura, Utada Hikaru (of course), the old neo-traditional group Rin', what I can catch from Yoko Shimomura (as his KH work is impeccable) -- same case for Keiichi Okabe (NieR), and jazz musician Keiko Matsui. Occasionally I'll grab something Euro-styled like E.S. Posthumus or Mediaeval Baebes.
Then I can handle very small amounts of the likes of Valshe, GARNiDELiA, Megumi Nakajima, Luna Haruna, ClariS, and maybe once every 3rd month I'll tolerate a Kyary Pamyu Pamyu song.