Not a band, but I like Ali Project. She (Arika) does a lot of anime OP/ endings.
My favorite ones are the 1st ending of Code Geass 勇俠青春謳 , and the last ever ending of Code Geass わが臈たし悪の華
.
I think Code Geass suits her style a lot.
I know she's famous for Rozen Maiden, but I don't think RM suits her style at all, lol.
Another exceptionally good one is the OP of Princess Resurrection 跪いて足をお嘗め
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