Man, I always hated the Rurouni Kenshin OP. It starts out great and then the singing starts...
Kekkai Sensen is great. It still feels like such a throwback series. Like something that would have been made in the late 90's. The character designs, story, setting, and music all feel different that most anime made these days. Which I guess makes complete sense once you learn it was created by the guy who made Trigun.